Methods for the detection of sequence amplification in the BRCA1 locus

ABSTRACT

Methods for detecting the amplifications of sequences in the BRCA1 locus, which sequences have ends consisting of or are framed with sequence stretches present at least twice in the BRCA1 locus, and which amplification results in at least two or at least three, especially three, tandem copies of the amplified sequence; methods for determining a predisposition to diseases or disorders associated with these amplifications, including predisposition to ovarian cancer or breast cancer and methods for detecting amplifications with similar features in other loci.

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BACKGROUND OF THE INVENTION

Field of the Invention

The invention relates to a method for detecting the amplifications of sequences in the BRCA1 locus, which sequences have ends consisting of or are framed with sequence stretches present at least twice in the BRCA1 locus, and which amplification results in at least two or at least three, especially three, tandem copies of the amplified sequence. This invention also relates to methods for determining a predisposition to diseases or disorders associated with these amplifications, including predisposition to ovarian cancer or breast cancer. This invention also relates to a method for detecting amplifications with similar features in other loci.

Description of the Related Art

Breast cancer is the most common malignancy in women, affecting approximately 10% of the female population. Incidence rates are increasing annually and it is estimated that about 1.4 million women will be diagnosed with breast cancer annually worldwide and about 460,000 will die from the disease. Germline mutations in the hereditary breast and ovarian cancer susceptibility genes BRCA1 (MIM#113705) and BRCA2 (MIM#600185) are highly penetrant (King et al., 2003), (Nathanson et al., 2001). BRCA1 and BRCA2 genes, together with other genes such as NBR2 gene have been identified, characterized and mapped in the human genome and these data are publicly available. Screening is important for genetic counseling of individuals with a positive family history and for early diagnosis or prevention in mutation carriers. When a BRCA1 or BRCA2 mutation is identified, predictive testing is offered to all family members older than 18 years. If a woman tests negative, her risk becomes again the risk of the general population. If she tests positive, a personalized surveillance protocol is proposed: it includes mammographic screening from an early age, and possibly prophylactic surgery. Chemoprevention of breast cancer with anti-estrogens is also currently tested in clinical trial and may be prescribed in the future.

Most deleterious mutations consist of either small frameshifts (insertions or deletions) or point mutations that give rise to premature stop codons, missense mutations in conserved domains, or splice-site mutations resulting in aberrant transcript processing (Szabo et al., 2000). However, mutations also include more complex rearrangements, including deletions and duplications of large genomic regions that escape detection by traditional PCR-based mutation screening combined with DNA sequencing (Mazoyer, 2005). Only one amplification involving more than two copies has been reported so far (Hogevorst et al., 2003). This amplification is a triplication in the 3′ portion of the BRCA1 gene, involving exons 17-19 and caused by Alu recombination.

Techniques capable of detecting these complex rearrangements include Southern blot analysis combined with long-range PCR or the protein truncation test (PTT), quantitative multiplex PCR of short fluorescent fragments (QMPSF) (Hofmann et al., 2002), real-time PCR, fluorescent DNA microarray assays, multiplex ligation-dependent probe amplification (MLPA)(Casilli et al., 2002), (Hofmann et al., 2002) and high-resolution oligonucleotide array comparative genomic hybridization (aCGH) (Rouleau et al., 2007), (Staaf et al., 2008). New approaches that provide both prescreening and quantitative information, such as qPCR-HRM and EMMA, have recently been developed and genomic capture combined with massively parallel sequencing has been proposed for simultaneous detection of small mutations and large rearrangements affecting 21 genes involved in breast and ovarian cancer (Walsh et al., 2010). Other techniques described for the detection of these complex gene rearrangements include Molecular Combing (Herrick and Bensimon, 2009); (Schurra and Bensimon, 2009); (Gad et al., 2001), (Gad et al., 2002a), (Gad et al., 2003); (Cheeseman et al. 2012); (U.S. 61/553,906).

Prior art methods are unable to detect and/or characterize amplifications when such amplifications involve more than one additional copy of the amplified sequence and/or when the amplified sequence includes portions of sequence present in multiple copies in the wild-type BRCA1 gene or surrounding locus and/or when the amplified sequence belongs to a portion of the BRCA1 locus with very high repeat content. Here, the inventors provide methods to detect and/or characterize such amplifications and to detect and/or characterize amplifications sharing similar features in other genomic loci.

BRIEF SUMMARY OF THE INVENTION

The BRCA1 and BRCA2 genes are involved, with high penetrance, in breast and ovarian cancer susceptibility. About 2% to 4% of breast cancer patients with a positive family history who are negative for BRCA1 and BRCA2 point mutations can be expected to carry large genomic alterations (in particular deletion or duplication) in one of the two genes, and especially BRCA1. However, some large rearrangements are missed by available techniques. This includes tandem amplification of sequences, characterized by the fact that more than one extra copy of the amplified sequence is introduced and/or characterized by the fact that the extremities of the amplified sequence (the sequence unit which undergoes repetition) are present in multiple copies—either perfectly or strongly homologous to each other—in the wild type locus, and/or when the amplified sequence is in a repeat-rich region.

Methods in vitro for detecting and/or characterizing these types of amplifications are one object of the invention. These include in vitro methods for detecting the triplication of a sequence fragment encompassing exons 1a, 1b and 2 of BRCA1 and fractions of the NBR2 gene. This region is particularly rich in Alu sequences and common copy number assessing techniques are unable to correctly characterize this triplication. The breakpoints of this tandem triplication share perfect sequence identity over 48 base pairs. This 48 base pair (bp) sequence is found in both BRCA1 and NBR2 genes in the reference human genome sequence.

The invention relates to tests or methods for this triplication and related amplifications, using Molecular Combing. This direct visualization approach allows immediate detection and characterization of these amplifications, and is not hindered by their repeat sequence content, homologous extremities or the number of copies. The invention also concerns tests or methods, which allow in vitro detection and characterization of this triplication and related amplification which are based on enrichment of a biological sample in specific DNA polynucleotides comprising the triplication. These methods are based on polymerase chain reaction (PCR), sequencing and other related techniques. Kits for performing such methods are also within the invention. The methods and kits bring substantial improvement over existing methods which are unable to detect such amplifications.

Results for four unrelated patients are disclosed, showing the triplication in all four patients' samples. The patients were also tested using other techniques of the prior art and the triplication could not be correctly detected or characterized, showing the substantial improvement the inventors brought to existing techniques.

The invention also concerns methods for determining predisposition (also designated as higher risk with respect to a population of reference) to ovarian or breast cancer based on these tests or methods. Furthermore, the inventors describe methods for adapting medical follow-up and/or treatment of patients with increased risk of breast or ovarian cancer and/or patients with ovarian breast cancer linked to this family of amplifications.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1: In silico-generated Genomic Morse Codes 4.0 (GMC 4.0) designed for high-resolution physical mapping of the BRCA1 genomic region. (A) The complete BRCA1 GMC 4.0 covers a genomic region of 200 kb and is composed of 14 signals (a1/a2, S1, Sex21, S2, S3Big, S4, S5, S6, Synt1, S7, S8, S9, b2/b3, S10) of a distinct color (not illustrated). Each signal is composed of 1 to 2 small horizontal bars, each bar corresponding to a single DNA probe. The region encoding the BRCA1 (81.2 kb) and NBR2 (19.5 kb) genes is composed of 8 “motifs” (m1b1-m8b1), Each motif is composed of 1 to 3 small horizontal bars and a black “gap” (no signal). (B) Zoom-in on the BRCA1 gene-specific signals and relative positions of the 24 exons.

FIG. 2: Molecular Combing analysis of breast cancer cell-line 10799001.

-   DNA isolated from EBV-immortalized B lymphocytes     (cell-line 10799001) co d from a breast cancer patient was analyzed     by Molecular Combing. -   (A) BRCA1 v 4.0 GMC computer simulation is shown at the top, the     BRCA1 signals obtained after microscopic visualization are shown at     the bottom. 3 microscopy signals are shown for each allele.

A triplication, visible as a tandem repeat triplication of the signal SYNT1 and the signal S7. The position of the detected triplication is indicated with vertical dotted lines. wt=wild type allele; mut=mutated allele bearing triplication.

(B) Same as (A), but with a different color for DNA probe S7, to confirm the nature of the probe involved in the mutation.

FIG. 3: Physical mapping of the Triplication of exons 1a, 1b and 2 in BRCA1. (A) Preliminary physical map derived by the Molecular Combing experiments and related measures. Above are the physical maps for the mutated allele (bearing the triplication) and the wild-type allele (corresponding to the reference human genome sequence), with a blown-up view below. The solid line represents the sequence left unchanged in the mutated allele, while the dotted line represents the sequence amplified in the mutated allele. The vertical wavy line is the estimated breakpoint position (and its replicates in the mutated allele). Synt1 and S7 designate full-length signals from the corresponding probes, while (Synt1) designates the partial signal arising from the Synt1 probe. Sizes indicated in by are the actual size of the probes and gap, while sizes in kb intervals are estimates from Molecular Combing experiments. Four primers are shown as representative examples of primer positioning for the amplification of the breakpoint. (B)-(C) DNA fragments derived after PCR performed in the cell-line 10799001 or the control cell-line 40.

FIG. 4: Exact physical mapping of the BRCA1 triplication of exons 1a, 1b and 2. (A) Diagram showing results of breakpoint sequencing: sequence identity between sequence data from the F7R7 PCR fragment and the reference human genome sequence is depicted by horizontal bars, with corresponding genomic coordinates.

FIG. 5: Optimized PCR reaction to screen for the BRCA1 triplication in clinical samples. (A) Fragments specific for the BRCA1 triplication were obtained out 8 primers pairs. One single DNA fragment, without any disturbing unspecific fragments, was found for primer pairs F5/R2, F5/R3 and F6/R3 in the mutation positive cell-line 10799001, but not in the control cell-line 38. (B) Specific amplification of PCR fragments from primer pairs F5/R2, F5/R3 and F6/R3 observed in 3 unrelated patients harboring the amplification. No PCR product was observed for two negative controls.

DETAILED DESCRIPTION OF THE INVENTION

The invention disclosed herein provides methods for testing in vitro the presence of an amplification of a genetic sequence (e.g. stretch of DNA) in a biological sample containing nucleic acid representative of chromosomes, in particular nucleic acid representative of human chromosome 17, and in particular genomic nucleic acid of chromosome 17 comprising:

-   -   submitting said biological sample to a procedure allowing         physical mapping of the region extending from exon 2 of the         BRCA1 gene to the NBR2 gene;     -   detecting more than two successive examples (copies)         (duplication or more, in particular triplication) of a 6 kb- to         8 kb-sequence extending from intron 2 of BRCA1 to the NBR2 gene.

The invention also provides kits for testing in vitro the presence of an amplification of a genetic sequence in a sample using the method described herein.

The term “nucleic acid” and in particular “nucleic acid representative of chromosomes” as used herein designates one or several molecules of any type of nucleic acid capable of being attached to and stretched on a support as defined herein, and more particularly stretched by using molecular combing technology. Nucleic acid, and in particular “nucleic acid representative of chromosomes” also designates one or several molecules of any type of nucleic acid capable of being amplified using PCR or PCR-related methods or capable of being sequenced using sequencing methods. Nucleic acid molecules include DNA (in particular genomic DNA, especially chromosomal DNA, or cDNA) and RNA (in particular mRNA). A nucleic acid molecule can be single-stranded or double-stranded but is preferably double stranded.

“Nucleic acid representative of a given chromosome” means that said nucleic acid contains the totality of the genetic information or the essential information with respect to the purpose of the invention, which is present on said chromosome. In particular, it is chromosomal DNA.

Physical mapping, as used herein, is the creation, employing molecular biology techniques, of a genetic map defining the relative position of particular elements such as specified sequence stretches, mutations or markers on genomic DNA. Physical mapping does not require previous sequencing of the analyzed genomic DNA. A physical map obtained by a physical mapping method may include information on the distances or approximate distances separating particular elements or may be limited to information regarding the succession of these elements, i.e. the order in which they appear in the genomic region of interest.

In particular embodiments, the method of the invention involves using FISH or Molecular Combing or related direct mapping methods to allow physical mapping of the region extending from intron 2 of BRCA1 to the NBR2 gene.

FISH: Fluorescent in situ hybridization.

Molecular Combing is a technique for direct visualization of single DNA molecules that are attached, uniformly and irreversibly, to specially treated glass surfaces. Prior to nucleic acid stretching, nucleic acid manipulation generally causes the strand(s) of nucleic acid to break in random locations. Molecular Combing has been described in WO 95/22056, WO 95/21939, WO 2008/028931 and in U.S. Pat. No. 6,303,296.

Molecular Combing and related direct mapping methods or Molecular Combing or related direct mapping methods, as used herein, designates methods, including Molecular Combing, functionally similar to Molecular Combing, in that they provide means to directly measure distances or approximate distances separating given sequences on single DNA fibers. For some methods, precise determination of the distance between specified sequences is possible. Precise measurement may be understood to provide a distance accurate to 10,000 bp (10 kb), 1,000 bp (1 kb), 100 bp, 10 bp or 1 bp. For other methods, only approximate distance measurements are possible. For other methods yet, only a succession of sequences on a DNA fiber may be determined, i.e. the order in which these sequences are arranged on the DNA fiber, such sequences being possibly present several times on the DNA fiber. While these methods may not always provide means to measure accurately the size of an amplified sequence as addressed herein, they can nevertheless usually detect such amplifications when designed following the method disclosed by the inventors. Molecular Combing and related direct mapping methods may rely on direct measurement of the physical distance between the specified sequences, or on measurement of a physical value directly related to the physical distance between the specified sequences. Such physical values include time, if e.g. the DNA fiber is made to move at a known speed through a detector recording the time of passage of the specified sequences. Such values also include total fluorescence intensity passing through a detector, when such total fluorescence intensity may be related to total nucleic acid content and the DNA fiber is made to move in a detector that can record fluorescence intensity comprised through specified sequences. Such methods may also provide the means for direct reading of the succession of sequences of interest, if e.g. the sequences of interest are labeled with distinct markers or distinct combinations of markers, fluorescent or otherwise, and the method provides means for reading the succession of markers, i.e. the order in which the markers are arranged on the DNA fiber.

In certain embodiments, Molecular Combing and related direct mapping methods are DNA stretching methods. The nucleic acid sample is generally stretched on a support in linear and parallel strands using a controlled stretching factor. By stretching factor it is meant herein the conversion factor allowing to connect physical distances measured on the stretched nucleic acid to the sequence length of said nucleic acid. Such a factor may be expressed as X kb/μm, for example 2 kb/μm. By controlled stretching factor it is meant herein a technique for which the stretching factor is sufficiently constant and uniform to allow reliable deduction of the sequence length of a hybridization signal from the measured physical length, with or without the use of calibration probes on the tested sample.

Other DNA stretching methods may be used as an alternative to Molecular Combing. These methods include, for example:

-   -   methods based on the extraction of DNA with detergent and/or         high salt concentration, combined or not with the incubation         with an intercalating agent and/or UV-light, derived from the         methods termed ECF-FISH (extended chromatin fibers-fluorescent         in situ hybridization), Halo preparation, and other methods         described in (Heng et al., 1992; Haaf and Ward, 1994; Wiegant et         al., 1992; Florijn et al., 1995; Vandraager et al., 1998, Raap,         1998, Palotie et al., 1996; Fransz et al., 1996); and     -   methods based on the stretching of DNA through the action of a         hydrodynamic flow or through mechanical traction on the DNA         molecules, by capillarity, gravity or mechanical force, possibly         in a micrometer- or nanometerscale device, the DNA being or not         immobilized on a solid support, derived from methods termed         DIRVISH (direct visual hybridization), optical mapping, and         other methods described in Parra and Windle, 1993; Raap, 1998;         Heiskanen et al., 1994; Heiskanen et al., 1995; Heiskanen et         al., 1996, Mann et al., 1996, Schwartz et al., 1993; Samad et         al., 1995, Jing et al., 1998; Dimalanta et al., Palotie et al.,         1996; Larson et al., 2006)

In particular embodiments, the method of detection of the invention comprising steps enabling Molecular Combing or related direct mapping method also comprises a hybridization step of nucleic acid representative of chromosome 17, with at least one probe or set of 2 probes or more allowing the identification of the region extending from intron 2 of BRCA1 to the 5′ region of NBR2. Hybridization with said probe(s) enables determination of presence of repetition in particular duplication or triplication of amplified sequence of the invention.

In a particular embodiment, the hybridization step is followed by an analysis of the resulting hybridization pattern, consisting of or comprising:

-   -   comparing the resulting hybridization pattern with the         theoretical hybridization pattern i.e., the hybridization         pattern expected for a wild-type sample;     -   in cases where said resulting hybridization pattern contains         additional signals when compared to said theoretical         hybridization pattern, concluding that the sample contains a         sequence amplification;     -   optionally, if the probes generating the additional signals         cannot be unambiguously identified, performing additional         hybridization steps with modified sets of probes allowing the         unambiguous identification of the probes generating the         additional signals;     -   optionally, if said additional signals consist of or comprise         several identical patterns, concluding that the sequence         amplification resulted in more than one additional copy of the         amplified signal.

In particular embodiments, the Molecular Combing or related direct mapping method comprises a hybridization step of nucleic acid representative of chromosome 17, with at least the following probes:

-   -   one probe or set of probes allowing the identification of the         intron 2 of the BRCA gene;     -   and one probe or set of probes allowing the identification of         the 5′ region of the NBR2 gene;     -   and optionally other probes to confirm the location and/or         identify unambiguously the probes or sets of probes above.

As defined herein, a “probe” is a polynucleotide, a nucleic acid/polypeptide hybrid, a nucleic acid/polypeptide hybrid or a polypeptide, which has the capacity to hybridize to nucleic acid representative of chromosomes as defined herein, in particular to RNA and DNA by base pairing with said nucleic acid representative of chromosomes which is thus the target for the probe. In a particular embodiment, the probe is substantially or fully complementary to the target nucleic acid and accordingly enables stable hybrids to be formed in stringent conditions of hybridization and detected. This term encompasses RNA (in particular mRNA) and DNA (in particular cDNA or genomic DNA) molecules as well as, peptide nuclear acid (PNA), and protein domains. Said polynucleotide or nucleic acid hybrid generally comprises or consists of at least 100, 300, 500 nucleotides, preferably at least 700, 800 or 900 nucleotides, and more preferably at least 1, 2, 3, 4 or 5 kb. For example probes of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 kb or more than 15 kb, in particular 30, 50 or 100 kb can be used. In a particular embodiment, the length of the probes used is ranging from 0.5 to 50 kb, preferably from 1 to 30 kb and more preferably from 1 to 10 kb, from 4 to 20 kb, from 4 to 10 kb, or from 5 to 10 kb. Said polypeptide generally specifically binds to a sequence of at least 6 nucleotides, and more preferably at least 10, 15, 20 nucleotides. As used herein, the sequence of a probe, when the probe is a polypeptide, should be understood as the sequence to which said polypeptide specifically binds. A probe specific for a given region of the genome or specific for a given sequence, as used herein, is a probe capable in certain conditions of hybridizing on said given region of the genome or on said given sequence while in the same conditions it does not hybridize to most other regions of the genome or to sequences significantly different from said sequence.

In a particular embodiment, the sequence of a probe is at least 99% complementary, i.e., at least 99% identical, or at least 99% similar to the sequence of a portion of one strand of the target nucleic acid to which it must hybridize.

The term “complementary sequences” in the context of the invention means “complementary” and “reverse” or “inverse” sequences, i.e. the sequence of a DNA strand that would bind by Watson-Crick interaction to a DNA strand with the said sequence.

Generally, a probe will be tagged or labeled with a marker, such as a chemical or radioactive market that permits it to be detected once bound to its complement. The probes described herein are generally tagged with a visual marker, such as a fluorescent dye having a particular color such as blue, green or red dyes. Some probes according to the invention are selected to recognize particular portions or segments of the BRCA1 gene and surrounding locus.

In a particular embodiment, the nucleic acid sample used for Molecular Combing or related direct mapping methods is genomic DNA, in particular total genomic DNA or more preferably chromosomal genomic DNA (nuclear genomic DNA), and/or fragments thereof. Said fragments can be of any size, the longest molecules reaching several megabases (thousands of kb). Said fragment are generally comprised between 10 and 2000 kb, more preferably between 200 and 700 kb and are in average of about 300 kb.

The nucleic acid sample used in the method of the invention can be obtained from a biological fluid or from a tissue of biological origin, said biological sample, including tissue, being isolated for example from a human (also called patient herein).

Sequence lengths are expressed herein in kb (kilo base pairs, i.e. 1000 base pairs) or by (base pairs). The length of genetic sequences is usually measured on double stranded nucleic acid and thus expressed in base pairs, where every base pair is made of one nucleotide on one strand and its complementary nucleotide on the other strand. If applied to a single-stranded nucleic acid, the measurement in base pairs is understood to correspond to the measurement of the corresponding double-stranded nucleic acid, i.e. the nucleic acid made of the single-stranded nucleic acid of interest paired with its reverse complementary nucleic acid.

In a particular embodiment, the invention consists of or comprises:

-   -   hybridizing a nucleic acid representative of chromosome 17 with         a set of probes including at least one probe or set of probes         allowing to identify the region extending from intron 2 of BRCA1         to the NBR2 gene or a portion of this region;     -   measuring the size of the region recognized by said probe or set         of probes;     -   comparing the measured size with the size of a single copy of         said region or said portion of said region,     -   in the case where the measured size is greater than the size of         a single copy of said region or said portion of said region,         concluding that the sample contains a sequence amplification in         said region;     -   and, optionally, if the measured size is greater than the         expected size of two tandem copies of said region or said         portion of said region, concluding that the sample contains a         sequence amplification in said region, with more than one         additional copy of the amplified sequence.

In a particular embodiment, the hybridization step is followed by an analysis step consisting of or comprising:

-   -   determining the location of the breakpoint on one end of the         amplified sequence and/or a confidence interval for the location         of said breakpoint;     -   determining the size of the amplified sequence and/or a         confidence interval for the size of the amplified sequence;     -   determining from the above location and size and/or confidence         intervals for the location and/or size the location and/or a         confidence interval for the location of the breakpoint at the         other end of the amplified sequence.

The invention disclosed herein also provides methods for testing in vitro the presence of an amplification of a genetic sequence in a patient's genome, such method comprising:

-   -   obtaining a DNA sample from the patient;     -   submitting the DNA sample to a procedure allowing physical         mapping of the genomic region extending from intron 2 of the         BRCA1 gene to the NBR2 gene;     -   detecting more than two successive copies of a 6 kb- to 8         kb-sequence extending from intron 2 of BRCA1 to the NBR2 gene.

The invention also provides kits for testing in vitro the presence of an amplification of a genetic sequence in a patient's genome using the method described in the previous paragraph.

Wild-type: this expression designates an unmodified sequence for a given gene or genomic region, i.e. the gene or genomic region bearing the sequence published in the reference human genome sequence. Since only large rearrangements are considered herein, where more than 1 kb of sequence have been modified (deleted, amplified, inverted or modified otherwise) relative to the reference sequence, the expression wild-type designates a sequence with less than 1 kb differing from the reference human genome sequence.

PCR: polymerase chain reaction

PCR and related methods: as used herein, this expression designates any method allowing the detection in a sample and optionally the quantification of one or several fragments of DNA characterized by the sequences of their extremities and itheir sizes. This includes but is not restricted to PCR, quantitative PCR, isothermal amplification (Gill and, Ghaemi, 2008), multiplex, ligation-dependent probe amplification (MLPA, Schouten et al., 2002)

Breakpoint: as used herein, this expression designates the position in the genome of the extremities of a rearrangement found in a DNA sample. This implies that on one side of a breakpoint, the sequence of the DNA sample is identical to the reference human genome sequence, while on the other side the sequence differs from the wild-type sequence. A sequence overlapping the breakpoint would also differ from the reference human genome sequence.

Reference human genome sequence: the reference sequence used herein is the human genome Build GRCh37/hg19. The sequence corresponding to positions 41,267,001 to 41,285,000 of the human reference genome sequence build GRCh37/hg19 of human chromosome 17 is provided as SEQ ID No. 22.

genomic position: genomic positions are given as nucleotide positions corresponding to the reference human genome numbering. Genomic coordinates is used herein with the same meaning. Unless otherwise specified, genomic coordinates or positions given herein are from chromosome 17. A genomic position is described herein as “upstream” of another position on the same arm of a chromosome if it is located closer to the centromere (e.g. has a smaller position number if both are on the “q” arm of chromosome 17). Conversely, a genomic position is described as “downstream” of another position on the same arm of a chromosome if it is located further from the centromere (e.g. has a larger position number if both are on the “q” arm of chromosome 17).

Adaptation of medical follow-up: as used herein, this expression designates the modification of medical or clinical surveillance for a patient when e.g. the risk of cancer in this patient or predisposition is increased relatively to the general population. For example, a periodic monitoring of biological or clinical characteristics may be advisable for the general population with a given frequency (e.g. in the case of breast cancer, mammographies may be recommended every 5 years), while this monitoring may be advisable with higher frequency for patients at elevated risk of a disease (e.g. in the case of an elevated risk or breast cancer, mammographies may be recommended every year). The adaptation of medical follow-up may be the prescription or recommendation of an adapted follow-up—whether the patient follows the prescription or recommendation or not —; the implementation of the adapted follow-up, or any other action performed aiming to adapt medical follow-up.

Predictive genetic testing: screening procedure involving direct analysis of DNA molecules isolated from human biological samples (e.g.: blood), used to detect gene mutations associated with disorders that appear after birth, often later in life. These tests can be helpful to people who have a family member with a genetic disorder, but who have no features of the disorder themselves at the time of testing. Predictive testing can identify mutations that increase a person's chances of developing disorders with a genetic basis, such as certain types of cancer.

Polynucleotides: This term encompasses naturally occurring DNA and RNA polynucleotide molecules (also designated as sequences) as well as DNA or RNA analogs with modified structure, for example, that increases their stability. Genomic DNA used for Molecular Combing will generally be in an unmodified form as isolated from a biological sample. Polynucleotides, generally DNA, used as primers may be unmodified or modified, but will be in a form suitable for use in amplifying DNA. Similarly, polynucleotides used as probes may be unmodified or modified polynucleotides capable of binding to a complementary target sequence. This term encompasses polynucleotides that are fragments of other polynucleotides such as fragments having 5, 10, 15, 20, 30, 40, 50, 75, 100, 200 or more contiguous nucleotides.

BRCA1 locus: This locus encompasses the coding portion of the human BRCA1 gene (gene ID: 672, Reference Sequence NM_007294) located on the long (q) arm of chromosome 17 at band 21, from base pair 41,196,311 to base pair 41,277,499, with a size of 81 kb (reference genome Build GRCh37/hg19), as well as its introns and flanking sequences. Following flanking sequences have been included in the BRCA1 GMC: the 102 kb upstream of the BRCA1 gene (from 41,277,500 to 41,379,500) and the 24 kb downstream of the BRCA1 gene (from 41,196,310 to 41,172,310). Thus the BRCA1 GMC covers a genomic region of 207 kb.

BRCA1 gene and surrounding locus: this expression designates herein the human genome portion containing the BRCA1 gene and ˜300 kb flanking portions on either side and corresponds to genomic positions 40,900,000 to 41,600,000.

Intron 2 of BRCA1: as used herein, this expression designates the genome region comprised between exon 2 and exon 3 of BRCA1, or between genomic positions 41,267,770 and 41,276,000.

NBR2 gene: this gene is mapped in the human genome reference sequence to positions 41,277,600-41,292,342. As used herein, the 5′ region of NBR2 is the genomic region comprised between positions 41,277,600 and 41,282,600

A sequence extending from intron2 of BRCA1 to the NBR2 gene: this expression designates a sequence having one extremity in the intron 2 of BRCA1 and one extremity in the NBR2 gene. Such a sequence would necessarily include exons 1a, 1b and 2 of BRCA1. Such a sequence would have one extremity located upstream of genomic position 41,276,000 and one extremity located downstream of genomic position 41,277,600.

Region extending from intron2 of BRCA1 to the NBR2 gene: this expression designates the human genome portion extending from genomic positions 41,270,000 (a position located between exons 2 and 3 of BRCA1) to 41,282,600 (a position located in the NBR2 gene).

Germline rearrangements: genetic mutations involving gene rearrangements occurring in any biological cells that give rise to the gametes of an organism that reproduces sexually, to be distinguished from somatic rearrangements occurring in somatic cells.

Amplified sequence encompasses within the invention a stretch of DNA which undergoes repetition (i.e. is copied) in a genome and in particular is repeated so that at least two identical stretches of said DNA, or at least three identical stretches of DNA are present in the considered genome or genomic locus. In particular, the considered stretch of DNA is duplicated (1 additional copy of the stretch of DNA are present, i.e., a same sequence is present two times in the genome or genomic locus) or triplicated (2 additional copies of the stretch of DNA are present, i.e. a same sequence is present three times in the genome or genomic locus). Tandem amplification: mutations characterized by a stretch of DNA that is duplicated to produce two or more adjacent copies, resulting in a tandem repeat array.

Tandem repeat array: a stretch of DNA consisting of two or more adjacent copies of a sequence. A single copy of this sequence in the repeat array is called a repeat unit. Gene amplifications occurring naturally are usually not completely conservative, i.e. in particular the extremities of the repeated units may be rearranged, mutated and/or truncated. In the present invention, two or more adjacent sequences with more than 90% homology are considered a repeat array consisting of equivalent repeat unit. Unless otherwise specified, no assumptions are made on the orientation of the repeat units within a tandem repeat array. Such repeat units within a tandem repeat array may be separated by less than 100, or less than 10, or less than 5 or 0 nucleotides that do not belong to the repeated sequence.

Complex Rearrangements: any gene rearrangement that can be distinguished from a simple deletion or a simple duplication. Examples are translocations or inversions, or combinations of several duplications, or combinations of deletions and duplications.

Detectable label or marker: any molecule that can be attached to a polynucleotide and which position can be determined by means such as fluorescent microscopy, enzyme detection, radioactivity, etc, or described in the US application nr. US2010/0041036A1 published on 18 Feb. 2010.

Primer: This term has its conventional meaning as a nucleic acid molecule (also designated sequence) that serves as a starting point for polynucleotide synthesis. In particular, Primers may have 20 to 40 nucleotides in length and may comprise nucleotides which do not base pair with the target, providing sufficient nucleotides in their 3′-end, especially at least 20, hybridize with said target. The primers of the invention which are described herein are used in pairs in PCR procedures, or individually for sequencing procedures.

Genomic Morse Code(s): A GMC is a series of “dots” (DNA probes with specific sizes and colors) and “dashes” (uncolored spaces with specific sizes located between the DNA probes), designed to physically map a particular genomic region. The GMC of a specific gene or locus is characterized by a unique colored “signature” that can be distinguished from the signals derived by the GMCs of other genes or loci. The design of DNA probes for high resolution GMC requires specific bioinformatics analysis and the physical cloning of the genomic regions of interest in plasmid vectors. Low resolution CBC has been established without any bioinformatics analysis or cloning procedure.

Repetitive sequences: the BRCA1 and BRCA2 gene loci contain repetitive sequences of different types: SINE, LINE, LTR and Alu. Such repetitive sequences are known to make molecular testing difficult due e.g. to non-specific binding of primers. Such repetitive sequences, and regions rich in repetitive sequences, are known to be prone to rearrangements, potentially due to homologuous recombination or similar mechanisms (van Binsbergen et al. 2011).

The term “sample” or “biological sample” as used herein relates to a material or mixture of materials, typically, although not necessarily, in fluid form, containing one or more components of interest. For Molecular Combing, the sample will contain genomic DNA from a biological source, in particular suitable for for diagnostic applications, usually obtained from a patient. The invention concerns means, especially polynucleotides, and methods suitable for in vitro implementation on samples.

The terms “nucleoside” and “nucleotide” are intended to include those moieties that contain not only the known purine and pyrimidine bases, but also other heterocyclic bases that have been modified. Such modifications include methylated purines or pyrimidines, acylated purines or pyrimidines, alkylated riboses or other heterocycles. In addition, the terms “nucleoside” and “nucleotide” include those moieties that contain not only conventional ribose and deoxyribose sugars, but other sugars as well. Modified nucleosides or nucleotides also include modifications on the sugar moiety, e.g., wherein one or more of the hydroxyl groups are replaced with halogen atoms or aliphatic groups, or are functionalized as ethers, amines, or the like.

The term “stringent conditions” as used herein refers to conditions that are compatible to produce binding pairs of nucleic acids, e.g., surface bound and solution phase nucleic acids, of sufficient complementarity to provide for the desired level of specificity in the assay while being less compatible to the formation of binding pairs between binding members of insufficient complementarity to provide for the desired specificity. Stringent assay conditions are the summation or combination (totality) of both hybridization and wash conditions.

A “stringent hybridization” and “stringent hybridization wash conditions” in the context of nucleic acid hybridization (e.g., as required for Molecular Combing or for identifying probes useful for GMC) are sequence dependent, and are different under different experimental parameters. Stringent hybridization conditions that can be used to identify nucleic acids within the scope of the invention can include for example hybridization in a buffer comprising 50% formamide, 5×SSC, and 1% SDS at 42° C., or hybridization in a buffer comprising 5.times.SSC and 1% SDS at 65° C., both with a wash of 0.2×SSC and 0.1% SDS at 65° C. Exemplary stringent hybridization conditions can also include a hybridization in a buffer of 40% formamide, 1M NaCl, and 1% SDS at 37° C., and a wash in 1×SSC at 45° C. Alternatively, hybridization to filter-bound DNA in 0.5 MNaHPO₄, 7% sodium dodecyl sulfate (SDS), 1 mM EDTA at 65° C., and washing in 0.1×SSC/0.1% SDS at 68° C. can be employed. Yet additional stringent hybridization conditions include hybridization at 60° C. or higher and 3×SSC (450 mM sodium chloride/45 mM sodium citrate) or incubation at 42° C. in a solution containing 30% formamide, 1 M NaCl, 0.5% sodium sarcosine, 50 mM IVIES, pH 6.5. Those of ordinary skill will readily recognize that alternative but comparable hybridization and wash conditions can be utilized to provide conditions of similar stringency.

A probe or primer located in a given genomic locus means a probe or a primer which hybridizes to the sequence in this locus of the human genome. Generally, probes are double stranded and thus contain a strand that is identical to and another that is reverse complementary to the sequence of the given locus. A primer is single stranded and unless otherwise specified or indicated by the context, its sequence is identical to that of the given locus. When specified, the sequence may be reverse complementary to that of the given locus. In certain embodiments, the stringency of the wash conditions that set forth the conditions that determine whether a nucleic acid is specifically hybridized to a surface bound nucleic acid. Wash conditions used to identify nucleic acids may include for example a salt concentration of about 0.02 molar at pH 7 and a temperature of at least about 50° C. or about 55° C. to about 60° C.; or a salt concentration of about 0.15 M NaCl at 72° C. for about 15 minutes; or a salt concentration of about 0.2×SSC at a temperature of at least about 50° C. or about 55° C. to about 60° C. for about 15 to about 20 minutes; or, the hybridization complex is washed twice with a solution with a salt concentration of about 2×SSC containing 0.1% SDS at room temperature for 15 minutes and then washed twice by 0.1×SSC containing 0.1% SDS at 68° C. for 15 minutes; or, equivalent conditions. Stringent conditions for washing can also be for example 0.2×SSC/0.1% SDS at 42° C.

A specific example of stringent assay conditions is rotating hybridization at 65° C. in a salt based hybridization buffer with a total monovalent cation concentration of 1.5 M followed by washes of 0.5×SSC and 0.1×SSC at room temperature.

Stringent assay conditions are hybridization conditions that are at least as stringent as the above representative conditions, where a given set of conditions are considered to be at least as stringent if substantially no additional binding complexes that lack sufficient complementarity to provide for the desired specificity are produced in the given set of conditions as compared to the above specific conditions, where by “substantially no more” is meant less than about 5-fold more, typically less than about 3-fold more. Other stringent hybridization conditions are known in the art and may be employed, as appropriate.

“Sensitivity” describes the ability of an assay to detect the nucleic acid of interest in a sample. For example, an assay has high sensitivity if it can detect a small concentration of the nucleic acid of interest in sample. Conversely, a given assay has low sensitivity if it only detects a large concentration of the nucleic acid of interest in sample. A given assay's sensitivity is dependent on a number of parameters, including specificity of the reagents employed (such as types of labels, types of binding molecules, etc.), assay conditions employed, detection protocols employed, and the like. In the context of Molecular Combing and GMC hybridization, sensitivity of a given assay may be dependent upon one or more of: the nature of the surface immobilized nucleic acids, the nature of the hybridization and wash conditions, the nature of the labeling system, the nature of the detection system, etc.

The invention thus relates to each and any of the following embodiments taken individually or in any combination. In particular, the invention concerns the following methods.

The invention relates to a method for in vitro detection of large rearrangement in the BRCA1 gene contained in nucleic acid of a biological sample comprising nucleic acid representative of chromosomal nucleic acid, in particular nucleic acid of human chromosome 17, comprising the step of detecting multiple copies of a target amplified sequence which is a sequence including exons 1a, 1b and 2 of the BRCA1 gene in the human 17 chromosome.

In a particular embodiment of the invention, the method for in vitro detection of large rearrangement in the BRCA1 gene contained in nucleic acid of a biological sample comprising nucleic acid representative of chromosomal nucleic acid, in particular nucleic acid of human chromosome 17, comprises the step of detecting multiple copies of a target amplified sequence which is a sequence having a size in a range of 6 kb to 8 kb and extending from intron 2 of the BRCA1 gene to the 5′ end of the NBR2 gene in the human 17 chromosome.

According to another embodiment, a particular method for in vitro detection of large rearrangement in the BRCA1 gene according to the invention comprises steps of:

-   -   providing the nucleic acid of the biological sample which         comprises the target amplified sequence in conditions that         enable hybridization with a probe or a set of probes, in         particular providing the nucleic acid of the biological sample         which comprises the target amplified sequence as isolated         nucleic acid;     -   contacting said provided nucleic acid with a probe or a set of         probes in conditions enabling hybridization of the probe(s) with         the target sequence, wherein each probe hybridizes with all or         part of the amplified sequence extending from intron 2 of the         BRCA1 gene to the 5′ end of the NBR2 gene,     -   detecting signals corresponding to hybridized probe(s), in         particular by visualization. In a preferred embodiment of the         method for in vitro detection of large rearrangement in the         BRCA1 gene according to the invention, the detected amplified         nucleic acid sequence is present in a copy number of at least 3         successive copies, in particular a copy number of 3 thereby         characterizing a triplication in tandem of the target amplified         sequence in the biological sample.

A method for in vitro detection of large rearrangement in the BRCA1 gene according to another particular embodiment of the invention, comprises a step wherein the detection of multiple copies of the target amplified sequences comprises measuring the size of the nucleic acid sequence hybridized to the probe(s) and comparing said measured size to the size of the amplified sequence taken as a single copy which is in a range of 6 kb to 8 kb.

In a further particular embodiment of a method for in vitro detection of large rearrangement in the BRCA1 gene according to the invention, the nucleic acid representative of chromosomal nucleic acid, in particular nucleic acid of human chromosome 17 is stretched prior to contacting with the probe(s).

The invention relates in a particular embodiment, to a method for in vitro detection of large rearrangement in the BRCA1 gene as defined herein, wherein the target sequence consists of the sequence extending from position 41,272,683 to position 41,279,942 in human chromosome 17 or a sequence framed by nucleic acid sequences consisting of the 48 base pairs sequence at position 41,272,683 in the BRCA1 gene and the identical sequence in the NBR2 gene.

A further particular embodiment of the method for in vitro detection of large rearrangement in the BRCA1 gene according to the invention is a method wherein the set of probes comprises or consists of a mixture of probes comprising Synt1 probe having a nucleic acid sequence base pairing with a genomic sequence starting with nucleotide at position 41,269,785 and ending with nucleotide at position 41,274,269 and S7 probe having a nucleic acid sequence base pairing with a genomic sequence starting with nucleotide at position 41,275,399 and ending with nucleotide at position 41,278,707, said probes being labeled with different markers or labels, in particular with a marker or label enabling visualization of a different color for each probe when detected.

A method for in vitro detection of large rearrangement in the BRCA1 gene according to a particular embodiment of the invention is a method wherein the Synt1 probe has the sequence amplified by primers Synt1F (SEQ ID No. 17) and Synt1R (SEQ ID No. 18) on a nucleic acid representative of the human BRCA1 gene or has the sequence of SEQ ID No. 1 and the S7 probe has the sequence amplified by primers S7F (SEQ ID No. 19) and S7R (SEQ ID No. 20) on a nucleic acid representative of the human BRCA1 and NBR2 genes or has the sequence of SEQ ID No. 2.

According to the definition of the invention provided herein, a particular method for in vitro detection of large rearrangement in the BRCA1 gene, comprises the steps of:

-   -   providing isolated nucleic acid representative of chromosomal         nucleic acid that comprises the target amplified sequence, in         particular isolated nucleic acid of human chromosome 17, in         particular isolated genomic DNA of human chromosome 17 in a         combing vessel;     -   performing molecular combing on said nucleic acid; to stretch         the nucleic acid and provide physical mapping of said stretched         nucleic acid;     -   contacting combed nucleic acid with a labeled probe or a set of         probes wherein each of the probe hybridizes with a distinct         region of the target amplified sequence and is labeled with a         different label, in conditions enabling hybridization of the         probes with the target amplified sequence;     -   washing the reaction mixture after hybridization;     -   detecting the signals corresponding to hybridized labeled         probes.

According to a further embodiment, a method for in vitro detection of large rearrangement in the BRCA1 gene of the invention is a method wherein the detection of signals corresponding to hybridized labeled probes of a set of probes encompasses detecting hybridization patterns and determining the succession of hybridized probes, their identity and their length.

According to a further embodiment of the invention, the method for in vitro detection of large rearrangement in the BRCA1 gene, further comprises a step of comparing the detecting hybridization patterns reflecting the succession of hybridized probes with the theoretical hybridization pattern (i.e. the hybridization pattern expected for a wild-type sample).

Another object of the invention is concerns a method for in vitro detection of large rearrangement in the BRCA1 gene which comprises:

-   -   contacting the nucleic acid representative of chromosomal         nucleic acid comprising the target amplified sequence, in         particular nucleic acid of human chromosome 17, in particular         genomic DNA, of the biological sample, with one or several         set(s) of amplification primers wherein the primers have a         nucleotide sequence selected as follows:     -   one forward primer (oriented from telomere to centromere)         located preferentially less than 5 kb, more preferentially less         than 2 kb, even more preferentially less than 1 kb and even more         preferentially less than 500 bp from the breakpoint location in         the BRCA1 gene (i.e. between genomic positions 41,279,990 and         41,284,990; preferentially between positions 41,279,990 and         41,281,990; more preferentially between positions 41,279,990 and         41,280,990 and even more preferentially between positions         41,279,990 and 41,280,490); and     -   one reverse primer (oriented from centromere to telomere))         located preferentially less than 5 kb, more preferentially less         than 2 kb, even more preferentially less than 1 kb and even more         preferentially less than 500 bp from the breakpoint location in         the NBR2 gene (i.e. between genomic positions 41,267,683 and         41,272,683; preferentially between positions 41,270,683 and         41,272,683; more preferentially between positions 41,271,683 and         41,272,683 and even more preferentially between positions         41,272,183 and 41,272,683); and where         the forward primer is located upstream of the reverse primer,     -   enabling PCR amplification or PCR-related amplification of the         target amplified sequence extending from exon 2 of the BRCA1         gene to the 5′ end of the NBR2 gene,     -   detecting the PCR amplified nucleic acid fragments or         PCR-related amplified nucleic acid fragments and optionally         sequencing them.

A method for in vitro detection of large rearrangement in the BRCA1 gene involving PCR amplification or PCR-related amplification as defined above is in particular a method wherein the primer sets are selected in the group of primer pairs having nucleotide sequences designated as F7/R7 (SEQ ID No3/SEQ ID No. 4), F9/R8 (SEQ ID No. 5/SEQ ID No. 6), F1/R1 (SEQ ID No. 7/SEQ ID No. 8), F1/R2 (SEQ ID No. 7/SEQ ID No. 10), F1/R3 (SEQ ID No. 7/SEQ ID No. 12), F2/R7 (SEQ ID No. 9/SEQ ID No. 4), F3/R4 (SEQ ID No. 11/SEQ ID No. 14), F3/R7 (SEQ ID No. 11/SEQ ID No. 4), F4/R7 (SEQ ID No. 13/SEQ ID No. 4), F5/R2 (SEQ ID No. 15/SEQ ID No. 10), F5/R3 (SEQ ID No. 15/SEQ ID No. 12), F6/R3 (SEQ ID No. 16/SEQ ID No. 12), F7/R1 (SEQ ID No. 3/SEQ ID No. 8), and F7/R2 (SEQ ID No. 9/SEQ ID No. 10) F7/R3 (SEQ ID No. 3/SEQ ID No. 12) wherein the “F” primer is a forward primer and the “R” primer is a reverse primer or are selected in the group of primer pairs constituted by the reverse complementary sequences of the above sequences in the primer pairs.

In a particular embodiment of the method for in vitro detection of large rearrangement in the BRCA1 gene involving PCR amplification or PCR-related amplification as defined herein, the primer sets are selected in the group of primer pairs having nucleotide sequences designated as F7/R7 (SEQ ID No3/SEQ ID No. 4), and F9/R8 (SEQ ID No. 5/SEQ ID No. 6) in the group of primer pairs constituted by the reverse complementary sequences of the above sequences in the primer pairs.

Based on the methods defined herein, the invention also relates to a method of in vitro determining predisposition to disease associated with amplification of sequences in the BRCA1 locus of human chromosome 17 in a biological sample obtained from a human patient, which comprises performing a method of detection of large rearrangement in the BRCA1 gene in said biological sample as defined herein.

In particular, such a method is a method for the determination of predisposition to breast cancer or ovarian cancer, wherein said predisposition is acknowledged when an amplification, especially a triplication of the target amplified sequence is observed.

In a further embodiment the invention concerns a method of determining or adapting medical follow-up and/or treatment of a breast cancer or an ovarian cancer, which comprises performing a method of detection of large rearrangement in the BRCA1 gene in said biological sample as defined herein.

The invention also concerns a primer pair wherein the forward and the reverse primers have respectively a sequence selected from:

-   -   for the forward primer (oriented from telomere to centromere) a         sequence located preferentially less than 5 kb, more         preferentially less than 2 kb, even more preferentially less         than 1 kb and even more preferentially less than 500 bp from the         breakpoint location in the BRCA1 gene (i.e. between genomic         positions 41,279,990 and 41,284,990; preferentially between         positions 41,279,990 and 41,281,990; more preferentially between         positions 41,279,990 and 41,280,990 and even more preferentially         between positions 41,279,990 and 41,280,490); and     -   for the reverse primer (oriented from centromere to telomere)) a         sequence located preferentially less than 5 kb, more         preferentially less than 2 kb, even more preferentially less         than 1 kb and even more preferentially less than 500 bp from the         breakpoint location in the NBR2 gene (i.e. between genomic         positions 41,267,683 and 41,272,683; preferentially between         positions 41,270,683 and 41,272,683; more preferentially between         positions 41,271,683 and 41,272,683 and even more preferentially         between positions 41,272,183 and 41,272,683). A primer pair         selected from the group of primer pairs having nucleotide         sequences F1/R1 (SEQ ID No. 7/SEQ ID No. 8), F1/R2 (SEQ ID No.         7/SEQ ID No. 10), F1/R3 (SEQ ID No. 7/SEQ ID No. 12), F2/R7 (SEQ         ID No. 9/SEQ ID No. 4), F5/R2 (SEQ ID No. 15/SEQ ID No. 10),         F5/R3 (SEQ ID No. 15/SEQ ID No. 12), F6/R3 (SEQ ID No. 16/SEQ ID         No. 12) and F7/R2 (SEQ ID No. 9/SEQ ID No. 10) or in the group         of primer pairs constituted by the reverse complementary         sequences of the above sequences in the primer pairs.

The invention also concerns a mixture of probes comprising at least two labeled polynucleotides wherein each of the polynucleotides has a nucleotide sequence hybridizing with a nucleic acid sequence from the region extending from intron 2 of the BRCA1 gene to the NBR2 gene in human chromosome 17 and wherein each polynucleotide is labeled with a different visually detectable label.

In a particular mixture of polynucleotide probes of the invention, the polynucleotides have a nucleic acid sequence selected in the group of Synt1 (SEQ ID No. 1) and S7 (SEQ ID No. 2). The invention also relates to a kit for the detection of multiple copies of an amplified sequence having a size in a range of 6 kb to 8 kb and extending from intron 2 of the BRCA1 gene to the NBR2 gene in the human 17 chromosome in a biological sample comprising:

-   -   a primer pair selected from the group of primer pairs having         nucleotide sequences F1/R1 (SEQ ID No. 7/SEQ ID No. 8), F1/R2         (SEQ ID No. 7/SEQ ID No. 10), F1/R3 (SEQ ID No. 7/SEQ ID No.         12), F2/R7 (SEQ ID No. 9/SEQ ID No. 4), F5/R2 (SEQ ID No. 15/SEQ         ID No. 10), F5/R3 (SEQ ID No. 15/SEQ ID No. 12), F6/R3 (SEQ ID         No. 16/SEQ ID No. 12) and F7/R2 (SEQ ID No. 9/SEQ ID No. 10);     -   optionally, a detection probe for the PCR-amplified nucleotide         fragments, reagents for conducting PCR amplification or PCR-type         amplification;

instructions for use and packaging material.

Another object of the invention is an isolated polynucleotide comprising at least two or at least three tandem copies of a sequence, each copy having a size in a range of 6 kb to 8 kb and corresponding to a sequence extending from intron 2 of BRCA1 to the NBR2 gene in the human 17 chromosome.

Further aspects and characteristics of the invention are disclosed in the examples and in the figures.

EXAMPLES

1. Materials and Methods

Preliminary Patient Screening

Total human genomic DNA was obtained from the EBV-immortalized lymphoblastoid cell lines nr.10799001, 38 and 40 obtained from the Institut Curie (Paris), Preliminary screening for large rearrangements was performed with the QMPSF assay (Quantitative Multiplex PCR of Short Fluorescent Fragments) in the conditions described by Casilli et al and Tournier et al (Casilli et al., 2002) and by MLPA (Multiplex Ligation-Dependent Probe Amplification) using the SALSA MLPA kits P002 (MRC Holland, Amsterdam, The Netherlands) for BRCA1 and P045 (MRC-Holland) for BRCA2. The patient gave his written consent for BRCA1 analysis.

Molecular Combing

Sample Preparation

Total human genomic DNA was obtained from EBV-immortalized lymphoblastoid cell lines. A 45-μL suspension of 106 cells in PBS was mixed with an equal volume of 1.2% Nusieve GTG agarose (Lonza, Basel, Switzerland) prepared in 1×PBS, previously equilibrated at 50° C. The plugs were left to solidify for 30 min at 4° C., then cell membranes are solubilised and proteins digested by an overnight incubation at 50° C. in 250 μL of 0.5 M EDTA pH 8.0, 1% Sarkosyl (Sigma-Aldrich, Saint Louis, Mo., USA) and 2 mg/mL proteinase K (Eurobio, Les Ulis, France), and the plugs were washed three times at room temperature in 10 mM Tris, 1 mM EDTA pH 8.0. The plugs were then either stored at 4° C. in 0.5 M EDTA pH 8.0 or used immediately. Stored plugs were washed three times for 30 minutes in 10 mM Tris, 1 mM EDTA pH 8.0 prior to use.

Probe Preparation

All BRCA1 probes were cloned into pCR2.1-Topo or pCR-XL-Topo (Invitrogen) plasmids by TOPO cloning, using PCR amplicons as inserts. Amplicons were obtained using bacterial artificial chromosomes (BACs) as template DNA. For BRCA, the 207-kb BAC RP11-831F13 (ch17: 41172482-41379594, InVitrogen, USA) was used for probe cloning. Whole plasmids were used as templates for probe labelling by random priming. Briefly, for biotin (Biot) labeling, 200 ng of template was labelled with the DNA Bioprime kit (Invitrogen) following the manufacturer's instructions, in an overnight labelling reaction. For Alexa-488 (A488) or digoxigenin (Dig) labeling, the same kit and protocol were used, but the dNTP mixture was modified to include the relevant labeled dNTP, namely Dig-11-dUTP (Roche Diagnostics, Meylan, France) or A488-7-OBEA-dCTP (Invitrogen) and its unlabelled equivalent, both at 100 μM, and all other dNTPs at 200 μM. Labelled probes were stored at 20° C. For each coverslip, 5 μL of each labelled probe ( 1/10th of a labelling reaction product) was mixed with 10 μg of human Cot 1 and 10 μg of herring sperm DNA (both from Invitrogen) and precipitated in ethanol. The pellet was then resuspended in 22 μL of 50% formamide, 30% Blocking Aid (Invitrogen), 1×SSC, 2.5% Sarkosyl, 0.25% SDS, and 5 mM NaCl.

Synt1: the Synt1 probe described herein is the result of a PCR amplification using BAC RP11-831F13 as a template and the two following primers: Synt1-F (TTCAGAAAATACATCACCCAAGTTC) (SEQ ID NO:17) and Synt1-R (TACCATTGCCTCTTACCCACAA) (SEQ ID NO: 18). The predicted sequence of the Synt1 probe is as follows (corresponding to genomic coordinates 41,269,785-41,274,269):

(SEQ ID NO: 1) TTCAGAAAATACATCACCCAAGTTCCCATCCCTACCTGTCTATCCACAAA ACCAAGGCATTCCTGAGATTAGTTCATTTATTATACTAATATAACAAGTG TTTATTAAGTATCTACTACTATATTCAAGTACTATTCTAGGAGATAGAAA TGTAGCAGTTTACAAAATAAAGCCTGCTCTCATAGAGCTCATATTCTAGT GTGGTAGACAGTTGATACGGAATTAAAGAATACATGGGAATAAGTGCATT AAAGAGAAAAATTAAGCAGGGTAAGGGGAAACAGGTAGTTCAATATCTAT GTGGGGGTGAGATGTACATGGGGGGAGTCAGGAAAGGTTTCACTGAGGTG AGACTAGAGGATAGCTTAATAATGTAAAGAAACACACTATGCAACAATTA GGGGAAGAGCATTCCAAGAAAGAGGGAGCAGAGAAGGCAAACCCTGAGCA GGACCATGCCTGTGTATGCAGGACATCAGATAGGTCAAGGTGCTAAAATG TAATAATCCAGGAGGATATTGTAGGGAAAGACTATCAGAGAGGTAGCTGG TAACTTCTGGTAGGAACCTATAGGCTATTTTAAATCTTTAGCTTTATTCT GGTCTTTTTAATTTTCTTTTTTTTTTTCAGACAGAGTCTCGTTCTGTCGC CCAGGCTGGAGTGCAGTGGCACCATCTCGGCTCTCTGTAACCTCCGCCTC CTGAATTCAAGTGATTCTCCTGCCTCAGCCTCCCGAGTAGCTGGGACTAA AGGCATGCACCACCATGCCTTGGCCTCCCAAAGTACTGGGATTACAGGAG TGAGCCACCATGCCAGCCATCTTTTTAATTTTTAATGTTAATTAATTTTT GTAGAGACAGGATCTCACTATGATGCCCATGCTGGTCTTGAATGCCTGGC ATCAAGCAATCTTCCTGCTTCGGCTTCCCAAAGTGCTGGGATTACAGGTG TGAGCTACTATACCCGGCCTTTAGCTTTCTTCTGAATGTGAACCTTTTTT TTTTTTTTTGGAGATGGAGTCTCACTCACTCTGCTGCTCAGGCTGGAGTG CAGTGGTGTGGTCTTGGCTCACTGCAACCTCTGCCTCTCGGATTGAAGTG ATTCTTGTGCCTCAGCATTCCAAGTAGCTGGGACTACAGGCGCGTGCTGC CACACCCGGCTAATTTTTTTGTATTTTTGGTAGGGAAGGGGTTTCACCAT ATTGCCCAGGCTGGTCTTGAAGTCCTGACCTCAAGTGATCCATCTGCCTC GACCGGGATTACAGGCGTGAGCCACTACACTTAGCTCTAAATGTGAATTT TTGAAACGGATTTTTTGGATAAAGTCCAGGCAAGATATCAAAGAACGACT AACCTGGCAGTGTGACAAGAATGTGGTTTTTTCCTTAAATATTTAACTTT TTAGAAAAGGATCACAAGGGCCAGGTGCGGTGGCTCACGCTGTAATCCCA GCATTTTGGGAGGCCAAGGCGGGCCAGCCTGGGTGACAGAGAATCCATCT CAAAAAAAGAAAAAAAAAAAAGAAAAGGATCACAAGAAAAGCTTGTGGAC AGTAACCTTATTGTGAAGGGTTGTAATACAACTCTTGTAATCATGGGGTT TTTGACATAGCACAGGGCAGTGAAAAGAAAAACAATGAACTAAGTCAGGA GGCTGGGTTTCTACTACCAGTTGTGTATATAAGCAGAGCCACCTTGGGCT AACCACTCTACCTGAACCTGTTTCCTTCTCTTGCCATTCACCCTGCCAGA CTCCTTGGGCTATTGCAAGAATAAAATTAAATGCTACTTGGGAAAATGCT TCACAACCTGAGATGACTTGGGAAAAATGCTTCACAACCTGAGATAACTT GTACCAACATTGGTATTATTACTGGGACCAAATGTGACTTTAAAAAGAAA AACAACCTTGACAAAGAAAACTCTGATTGGTTACTAAATCCCTATTTCTG AGATAAGCTACATTTCAAAGAAATTCTCCGTAAAAGAAAAATTGGATTCA GTTATCATACCAGATGGCTTTCATTCTCACCACTGACTCAATTCTGAAAC AATTATATTTCAGTATGGTAATTATAATCTAAACTATATAAACACACTGT AAACACAAACTTTGAACAGATGAAAACTCCGATATGTAAAAAGGTAATGA ATGTTGAAGGAAGACTGTGAAAAGGGAAAAGAAAAAAAATTAAAATGTTC CCCTTCTAGGTCCTGATGAGAGTAAATGTTTACTATAAAAATGATTCAAA TATTTTAAACACTTTTCAAACCAGGCAATATTTTAGGCCTACTGTATATT TGCATTTTGAGCTTCCAATACGGATAAGTGACTGGAAAAAGCAGCTAGGT TTAGGTTGAAAAACAACAACCCACCGGGGAACACATTTTAGCAAATTCTT CTGAAAGTCAAAAATGTTATAGTCATAGGTAAAAAGTTACAAAGAACTAC CAATTGTCAGAAATAGCTGCCAATATTGACTTAGAAGACAGCAGAAGGAA TTTTAGTTCAAGAAACCTAAAACAGGCTGAAAACCTTACCTACCCTATAG CTACCACAAATAACACTGTTTCCAGTCATGATCATTCCTGATCACATATT AAGACATAACTGCAAATTGTGCTATACTGTACTATATTAAAAGGAAGTGA AATATGATCCCTATCCTAGAACTTTCCATACAAATGAATGTAAAACACCA TAAAAATTAATCTTAAGGCCGGGCGCGGTGGCTCACGCCTGTAATCCCAG CACTTTGGGAGGCCGAGGTGGGCGGATCACGAGGTCAGGAAGTGGAGACC ATCCTGGCTAACACGGTGAAACCCCGTCTCTACTAAAAATACAAAAAATT AGCCGGGCGTGGTGGTGGACGCCTGTAGTCCCAGCTACTTGGGGGGCCGA GGCAGGAGAATGGCGTGAACCCGGGAGGCGGAGCTTGCAGTGAGCCGAGA TGGCGCCACTGCACTCCGGCCTGGGTGAAAGAGCGAGACTCCGTCTCAAA AACAAAACAAACAAAAATTAATCTTAAGCCAGGCGCAGTGGCTCACGCCA GCACTTTGGAAGGCCGAGGCGGGTGGATCACGAGATCAGGACTTCAAGAC CAGCCTGACCAACGTGATGAAACCCTATCTCTACTAAAAATACAAAATTA GCCGGCCACGGTGGCGTGCGCCTATAATCCCAGCTACTCAGGAGGCTGAG GCAGGAGAAGCGCTTGAACTTGAACCTGGCAGGCGGAGGTTGCAGTGAGC CAAGATGGCGCCACTGCACTCCAGCCTGGGCGACAGAGCCAGACTCCAAC CCCCCACCCCGAAAAAAAAAGGTCCAGGCCGGGCGCAGTGGCTCAGGACT GTAATCCCAGCACTTTGGAAGGCTGAGGCGGGTGGATCACAAGGTCAGGA GATCGAGACCATCTTGGCTAACATGGTGAAACCCCGTCTCTACTAAAAAT ACAAAAAATTAGCCGGGCATAGTGGTGGGCGCCTGTAGTCCCAGCTACTC GGGAGGCTGAGGCAGGAGAATGGCCTGAACCCGGGAGGCGGAGCTGGCAG TGAGCCAAGATCGTGCCACTGCACTCCAGCCTAGGCAGCAGAGCGAGACC GTGTCTCAAAAAAACAAAACAAAACAAAACAAAAAGTCTGGGAGCGGTGG CTCACGCCTGTAATCCCAGCACTTTCGGAGGCCAAGGCAGGAGGATCACC TGAGGTCAGGAGTTCGAGACCAACCTGACCAATATGGAGAAACCCTGTCT CTACTAAAAATACAAAATTAGCTGGTGTGATGGCACATGCCTGCAATCCC AGGTACTCCGGAGGCTGAGGCAGCAGAATTGCTTGAACCCGGGAGGTGGA GGTTGTAGTGAGCCGAGATTGTGCCACTGCACTCCAGCCTGGGCAACAAG AGCCAAAGTCTGTCTCAAAAAAAAAAAAAAAAAAAAAAAAAGAAATTAAT CTTAACAGGAAACAGAAAAAAGCAATGAAAAGCTAGAAAACATAATAGTT GATTGAAAATAACAATTTAGCATTTTCATTCTTACATCTTTAATTTTTAT GTATCTGAGTTTTTAATTGATGGTTTAATTTGCCAGAATGAGAAAGAACA TCCTATTTTTATGACTCTCTCCCATGGAAATGAAACATAAATGTATCCAA ATGCCACACTATTGAGGATTTTCCTGATCACTGATTGTCATGAGTAAGTT TTGTGCTTTTTCAAAAGCAGTTTTTTCCTACAATGTCATTTCCTGCTTCT CTGGCTCTGATTTTCAATAAATTGATAAATTGTGAATCCTGTTTTCCTCT TATTTTTGTTTAGCTATAATGTTGAAGGGCAAGGGAGAGGATGGTTATTT ATAAATCTTGTATCGCTCTGAAAACACAACATACATTTTCCTTAATCTGA TTAACTTGACTTCAAATATGAAAAACAACTTTCATAAAGCAGAAAAGAAT TTACCCTTTTTTATTGTGGGTAAGAGGCAATGGTA

S7: the S7 probe described herein is the result of a PCR amplification using BAC RP11-831F13 as a template and primers corresponding to the reference human genome sequence at positions 41,275,399 (forward primer: GAGTTTAGCTCTGTCGCTGGA) (SEQ ID NO:19) and 41,278,707 (reverse primer: TGCTAGCACGTTGTCACCTC) (SEQ ID NO:20). The predicted sequence of the S7 probe is as follows (corresponding to genomic coordinates 41275399-41278707):

(SEQ ID NO: 2) AGTTTAGCTCTGTCGCTGGAGTTCAGTGGTGCCATATTGGCTCACAGCAA CATCTGCCTCCTGGTTCAAGTGATTCTCCTGCCTCAGCCTCCTGAGTAGC TGGGATTACAGGCACATGCCACTACGCCCAGCTAATTTTTGTATTTTTAG TGGAGAGGGGGTTTCACCATGTTGGCCAGGATGGTCTCGATCTCCTGACC TCGTGATCCTACCACCTTGGCCTCCCAAAGTGCTGGGATTACAGGCATAA GCCACCGCCCTCGGCCTCATCCATGATTTTATTTTGCCATTTCAAGTGAT GGAGCTTGTTTTAGAGCTGGAAGAAAAGCCAAAATGCCAGTTAATCTAAA CTAGATTCCTGCCCCAGTGCAGAACCAATCAAGACAGAGTCCCTGTCTTT CCCGGACCACAGGATTTGTGTTGAAAAGGAGAGGAGTGGGAGAGGCAGAG TGGATGGAGAACAAGGAATCATTTTCTATATTTTTAAAGTTCTTCAGTTA AGAAAATCAGCAATTACAATAGCCTAATCTTACTAGACATGTCTTTTCTT CCCTAGTATGTAAGGTCAATTCTGTTCATTTGCATAGGAGATAATCATAG GAATCCCAAATTAATACACTCTTGTGCTGACTTACCAGATGGGACACTCT AAGATTTTCTGCATAGCATTAATGACATTTTGTACTTCTTCAACGCGAAG AGCAGATAAATCCATTTCTTTCTGTTCCAATGAACTTTAACACATTAGAA AAACATATATATATATCTTTTTAAAAGGTTTATAAAATGACAACTTCATT TTATCATTTTAAAATAAAGTAAATTTAAGATTTGGAAGGTTTTAGAATAA TACAAACCAAAGAACTAATGACAACGTCCTTTATTTTTAAAGATTCTAGA AGTTGCTTTTTGTAATTAGACAACATAAATTCTGAATTTTTTCACATATT GCTGCCAACCCCTTGGGTCTTTTCCTTTCTCCAAGAAAGAGAAAGCTACA GAGGAGTGACTGACCGGGTAGGTGGTGGTAGCCTTAGCTTTCTCCAATGT TTCTGGTTGTTTTCTTTTTCTTGCATAAAACCAAAATCAACAACGACCAA ACCAACACCAATCAAGGCCTCCCCGCCCCTAACCTTTCCCAGTGACCTGC TCTCATCTCTGGATCCTCCTCAAGCACATCCCTGCCGGCAGCATCTGTTA CTACTGACGCTCCTCTACTTCCCTCTTGCGCTTTCTCAATGGCGCAAATG GATCCAGTTCTTAAGTTCTCCCTCCCACAAAATCCTGTCTCCTCCCCTTC CCAGACATATTCCTGGCACCTCTTCTTCCACAAGGTCCCATCCTCTCATA CATACCAGCCGGTGTTTTTTGTTTTGTTTTGTTTTGTTTTGTTTTGAGAC AGTCTCGCTCTGTCGCCCAGGCTGGAGTGCAATGGCGCGATCTCGGCTCA CTGCAACCTCCGCCTCCCGGGTTCTAGCGATTCTCCTGCCTCAGCCTCCT GAGTAGCTGGAGCGGCACCACGCCCGGCTAATTTTTGTATTTTTAGTAGA GACGGAGTTTCACCACGTTGGTCAGGCTGGTCTGGAACTCCTGACCTCAT GACCAGCCGACGTTTTTAAAGACATAGTGTCCCCCTCAAGGCATATTCCA GTTCCTATCACGAGGATTCCCCCACGGACACTCAGTGCCCCCTTCCTGAT CCTCAGCGCTTCCCTCGCGACCTACAAACTGCCCCCCTCCCCAGGGTTCA CAACGCCTTACGCCTCTCAGGTTCCGCCCCTACCCCCCGTCAAAGAATAC CCATCTGTCAGCTTCGGAAATCCACTCTCCCACGCCAGTACCCCAGAGCA TCACTTGGGCCCCCTGTCCCTTTCCCGGGACTCTACTACCTTTACCCAGA GCAGAGGGTGAAGGCCTCCTGAGCGCAGGGGCCCAGTTATCTGAGAAACC CCACAGCCTGTCCCCCGTCCAGGAAGTCTCAGCGAGCTCACGCCGCGCAG TCGCAGTTTTAATTTATCTGTAATTCCCGCGCTTTTCCGTTGCCACGGAA ACCAAGGGGCTACCGCTAAGCAGCAGCCTCTCAGAATACGAAATCAAGGT ACAATCAGAGGATGGGAGGGACAGAAAGAGCCAAGCGTCTCTCGGGGCTC TGGATTGGCCACCCAGTCTGCCCCCGGATGACGTAAAAGGAAAGAGACGG AAGAGGAAGAATTCTACCTGAGTTTGCCATAAAGTGCCTGCCCTCTAGCC TCTACTCTTCCAGTTGCGGCTTATTGCATCACAGTAATTGCTGTACGAAG GTCAGAATCGCTACCTATTGTCCAAAGCAGTCGTAAGAAGAGGTCCCAAT CCCCCACTCTTTCCGCCCTAATGGAGGTCTCCAGTTTCGGTAAATATAAG TAATAAGGATTGTTGGGGGGGTGGAGGGAAATAATTATTTCCAGCATGCG TTGCGGAATGAAAGGTCTTCGCCACAGTGTTCCTTAGAAACTGTAGTCTT ATGGAGAGGAACATCCAATACCAGAGCGGGCACAATTCTCACGGAAATCC AGTGGATAGATTGGAGACCTGTGCGCGCTTGTACTTGTCAACAGTTATGG ACTGGAGTGTTATGTTTTCGTATTTTGAAAGCAGAAACTAGGCCTTAAAA AGATACGTACAACTCTTTAGGGAGACTACAATTCCCATCCAGCCCCAGGA GTCTGGGGCAAGTAGTCTTGTAAGGTCAGTGGCCTGCGGGGACGCAGTGA GCGCCGAATTTGCCTGGGGCAGGGGAAATGCGCTCTGGCCCATGTCTGCG CACTCGTAGTTCCACCCCTCAGCCCCAGTGTTTGTTATTTTTCGGGTTCA GCTTGCTTTTGCCCCGTCTCCGTCGACGCAATCGCCACCAGTCAATGGGG TGGTCGTTTTGAGGGACAAGTGGTAAGAGCCAATCTTCTTGGCGAAAACG CGGAGAAACGGGACTAGTTACTGTCTTTGTCCGCCATGTTAGATTCACCC CACAGAGATAGCGGCAGAGCTGGCAGCGGACGGTCTTTGCATTGCCGCCT CCCCAGGGGGCGGGAAGCTGGTAAGGAAGCAGCCTGGGTTAGCTAGGGGT GGGGTCACGTCACACTAAGAGGGTTTGGAGAAGTTCAAGGGAGGAATCCT GCAAAGAAGAGGGGCGACTTTTTCCGTGTCTCCGGACAGCTAATCGTTTT AGTGACAGGATGAGAGAGCCCTTCGTGTTCTGAGGGACCGAGTGGGCGAA AAGCGCCGGAGAGTTGGAGAGTCTGTGGTTCAGAATGCGAGGTGACAACG TGCTAGCAG Genomic DNA Combing and Probe Hybridisation

Genomic DNA was stained by 1 h incubation in 40 mM Tris, 2 mM EDTA containing 3 μM Yoyo-1 (Invitrogen, Carlsbad, Calif., USA) in the dark at room temperature. The plug was then transferred to 1 mL of 0.5 M MES pH 5.5, incubated at 68° C. for 20 min to melt the agarose, and then incubated at 42° C. overnight with 1.5 U beta agarase I (New England Biolabs, Ipswich, Mass., USA). The solution was transferred to a combing vessel already containing 1 Ml of 0.5 M MES pH 5.5, and DNA combing was performed with the Molecular Combing System on dedicated coverslips (Combicoverslips) (both from Genomic Vision, Paris, France). Combicoverslips with combed DNA are then baked for 4 h at 60° C. The coverslips were either stored at −20° C. or used immediately for hybridisation. The quality of combing (linearity and density of DNA molecules) was estimated under an epi-fluorescence microscope equipped with an FITC filter set and a 40× air objective. A freshly combed coverslip is mounted in 20 μL of a 1 ml ProLong-gold solution containing 1 μL of Yoyo-1 solution (both from Invitrogen) Prior to hybridisation, the coverslips were dehydrated by successive 3 minutes incubations in 70%, 90% and 100% ethanol baths and then air-dried for 10 min at room temperature. The probe mix (20 μL; see Probe Preparation) was spread on the coverslip, and then left to denature for 5 min at 90° C. and to hybridise overnight at 37° C. in a hybridizer (Dako). The coverslip was washed three times for 5 mM in 50% formamide, 1×SSC, then 3×3 min in 2×SSC. Detection was performed with two or three successive layers of flurorophore or streptavidin-conjugated antibodies, depending on the modified nucleotide employed in the random priming reaction (see above). For the detection of biotin labelled probes the antibodies used were Streptavidin-A594 (InVitrogen, Molecular Probes) for the 1st and 3rd layer, biotinylated goat anti-Streptavidin (Vector Laboratories) for the 2nd layer; For the detection of A488-labelled probes the antibodies used were rabbit anti-A488 (InVitrogen, Molecular Probes) for the 1st and goat anti-rabbit A488 (InVitrogen, Molecular Probes) for the 2nd layer; For the detection of digoxygenin labelled probes the antibodies used were mouse anti-Dig (Jackson Immunoresearch) for the 1st layer, rat anti-mouse AMCA (Jackson Immunoresearch) for the 2nd layer and goat anti-mouse A350 (InVitrogen, Molecular Probes) for the 3rd Layer. We performed a 20 minutes incubation step at 37° C. in a humid chamber for each layer, and three successive 3 minutes washes in 2×SSC, 0.1% Tween at room temperature between layers. Three additional 3 minutes washes in PBS and dehydration by successive 3 minutes washes in 70%, 90% and 100% ethanol were performed before mounting the coverslip.

Image Acquisition

Image acquisition was performed with a customized automated fluorescence microscope (Image Xpress Micro, Molecular Devices, Sunnyvale, Calif., USA) at 40.times. magnification, and image analysis and signal measurement were performed with the softwares ImagaJ and JMeasure (Genomic Vision, Paris, France). Hybridisation signals corresponding to the BRCA1 probes were selected by an operator on the basis of specific patterns made by the succession of probes. For all motifs signals belonging to the same DNA fiber, the operator identified the ends of each segment and determined its identity and length (kb), on a 1:1 scale image. The data were then output in a spreadsheet. In the final analysis, only intact signals were considered, i.e. signals where no fiber breakage had occurred within the BRCA1 motifs.

Statistical Analysis

Molecular Combing allows DNA molecules to be stretched uniformly with a stretching factor close to 2 kb/μm (Michalet et al., 1997). For each motif, the following values were determined: the number of measured images (n), the theoretical calculated length (in kb), the mean measured length (kb), the standard deviation (sd, in kb), the coefficient of variation (CV, in %), the difference between measured and calculated length (delta, in kb).

2. Results

Design of the High-Resolution BRCA1 Genomic Morse Code v4.0

An electronic reconstruction of the designed BRCA1 GMC v4.0 is shown in FIG. 1. The BRCA1 GMC covers a region of 200 kb, including the upstream genes NBR1, NBR2, LOC100133166, and TMEM106A, as well as the pseudogene BRCA1P1. The complete BRCA1 GMC is composed of 14 signals, and to facilitate GMC recognition and measurement, signals on the BRCA1+ NBR2 genes were grouped together in 8 specific patterns called “motifs” (m1b1-m8b1).

Characterization by Molecular Combing of a Novel Tandem Repeat Triplication of Exons 1a, 1b and 2 in BRCA1

The presence of a large rearrangement on BRCA1 was first identified by visual inspection of the hybridization signals. A fraction of the detected signals showed a hybridization pattern differing from the normal pattern by the presence, between the S7 and S8 probe signals, of two additional pairs of signals corresponding to the color of the Synt1 and S7 probes (FIG. 2A). The signals were shown to arise from these probes by color swapping experiments, where the colors of some probes in the GMC are modified so as to observe the corresponding change in the hybridization signals. In one experiment, for example, the 87 probe was changed from green to blue and this resulted in the same change of color of the duplicated signal (FIG. 2B). The duplicated signal for the 87 probe was found to correspond to the full length of the 87 probe, while the additional signals for the Synt1 probe were found to correspond to only part of the Synt1 probe. This indicated the presence of a mutated allele, carrying an amplification of a region extending from the Synt1 probe to the gap between the S7 and S8 probes, along with an unmodified, wild-type allele in this sample.

Measurements were performed independently on signals from both alleles, the signals being attributed to either allele by the operator based on the hybridization pattern.

In one experiment, the SF was established from measurements of unmodified motifs (either from the wild-type allele or from unmodified regions in the mutated allele) to be 1.8 kb/μm. In the mutated allele, the distance from Synt1 to 88 was measured to be 38.5 kb, 14.9 kb longer than the expected size of 23.6 kb for a wild-type allele. This is expected to correspond to the measurement of the two extra copies of the amplified sequence, and the amplified sequence was thus determined to measure 7.4 kb. The 95% confidence interval for the size, calculated as 7.4 kb+/−2.sd√n (where n is the number of measurements used in the calculation), was found to be 6.6 kb-8.2 kb.

In another experiment, the size of the first and second additional pairs of signals corresponding to Synt1 and S7 were measured to be 6.6 kb and 7.0 kb, respectively (from one end of the additional Synt1 probe signal to the other end of the proximal S7 probe signal) and the size of the region spanning both pairs of additional signals was measured to be 14.2 kb (from one end of the first additional Synt1 probe signal to the other end of the second additional S7 probe). Measuring the pairs of signals possibly excludes part of the amplified sequence (the part comprised between the S7 probe and the S8 probe) and was therefore considered an underestimate of the amplified sequence. The difference between the sum of both pairs measured individually and the direct measurement of the region spanning both pairs is a measurement of the part of the amplified sequence comprised between the S7 and S8 probes. This was measured to be 0.64 kb on average with a 95% confidence interval, calculated as above, of 0.2 kb-1.1 kb.

The 95% confidence interval as above for the size of the region spanning both pairs measured directly, defined as above, is 13.4 kb-14.9 kb. This measurement corresponds to two copies of the amplified sequence, with the exclusion of one copy of the part of the amplified sequence comprised between the S7 and 88 probes. The 95% confidence interval for the size of the amplified sequence, when accounting for the part excluded from measurements using the determination above, is therefore 6.8 kb-8.0 kb.

Here, we report the identification and characterization of a triplication of a 6 kb-8.0 kb sequence, extending from intron 2 of the BRCA1 gene to the NBR2 gene. One extremity of the amplified sequence is within 2 kb of the extremity of the 87 probe (thus within genomic coordinates 41,278,700-41,280,700 in build hg19), while the other, as determined from the size of the amplified sequence is within genomic coordinates 41,270,700-41,274,700 in build hg19. This is the first report of a genomic amplification in this Alu-rich 5′-region of BRCA1, and the mutation is the second triplication reported so far in BRCA1. (Horgervost Cancer Research 2003, Sluiter Breast Cancer Research 2011).

3. Breakpoint Characterization of the BRCA1 Triplication by PCR and Sequencing

Based on our estimation of the location of the breakpoint, we designed PCR primer pairs in order to specifically amplify the sequence containing the breakpoint in the sample with the triplication.

PCR Amplification

PCR and were performed in 50 μL reactions. Cycling conditions were chosen according to the polymerase and the length of the sequence to amplify. The Taq polymerase Expand High Fidelity from Roche was employed using following PCR conditions for each reaction: 200 μM dNTP, 300 μM primers, 1.5 mM MgCl2, 2.6 U Taq. PCR amplification conditions were for the primer pairs F7/R7 and F9/R8: 10 cycles of (94° C. for 15 s, 57° C. for 30 s, 72° C. for 2 min), 30 cycles of (94° C. for 15 s, 57° C. for 30 s, 72° C. for 2 min), 72° C. for 7 min; for the other primer pairs: 95° C. for 5 min, 30 cycles of (94° C. for 30 s, 60° C. for 60 s, 72° C. for 1 min), 72° C. for 10 min. PCR products were analyzed on a 1% agarose gel containing SYBRsafe (InVitrogen) with 1 μg of the Marker Hyperladder 1 (Promega).

Primers have been designed with the Primer3 v.04.0 software and synthesized by MWG/Eurogentec. Primer sequences and temperature of annealing are the following:

(SEQ ID NO: 3) F7 5′-AGGGTTTCATCACGTTGGTC-3′ 58° C., (SEQ ID NO: 4) R7 5′-GCAAATGTAGTGGGGACTTG-3′ 57° C., (SEQ ID NO: 5) F9 5′-CTGCGCCTGGCTTAAGAT-3′ 57° C., (SEQ ID NO: 6) R8 5′-GATGTGGGTGGGGTCAGA-3′ 58° C., (SEQ ID NO: 7) F1 5′-ATAGGGTTTCATCACGTTGGTC-3′ 60° C., (SEQ ID NO: 8) R1 5′-CTAATCTGGTGGGCACTTGG-3′ 60° C., (SEQ ID NO: 9) F2 5′-GTCTTGAAGTCCTGATCTCGTG-3′ 59° C., (SEQ ID NO: 10) R2 5′-GTGTCTAGCTTGGGGTTTGG-3′ 60° C., (SEQ ID NO: 11) F3 5′-GAGATAGGGTTTCATCACGTTG-3′ 59° C., (SEQ ID NO: 12) R3 5′-CAGATGGGGACTTGGAAAAC-3′ 59° C., (SEQ ID NO: 13) F4 5′-GTTTCATCACGTTGGTCAGG-3′ 59° C., (SEQ ID NO: 14) R4 5′-CTGAGTCAGATGGGGACTTG-3′ 58° C., (SEQ ID NO: 15) F5 5′-GTTCAAGTTCAAGCGCTTCTC-3′ 59° C., (SEQ ID NO: 16) F6 5′-CTGCCAGGTTCAAGTTCAAG-3′ 58° C.

Following primers pairs were tested and validated by PCR: F7/R7 (SEQ ID No3/SEQ ID No. 4), F9/R8 (SEQ ID No. 5/SEQ ID No. 6), F1/R1 (SEQ ID No. 7/SEQ ID No. 8), F1/R2 (SEQ ID No. 7/SEQ ID No. 10), F1/R3 (SEQ ID No. 7/SEQ ID No. 12), F2/R7 (SEQ ID No. 9/SEQ ID No. 4), F3/R4 (SEQ ID No. 11/SEQ ID No. 14), F3/R7 (SEQ ID No. 11/SEQ ID No. 4), F4/R7 (SEQ ID No. 13/SEQ ID No. 4), F5/R2 (SEQ ID No. 15/SEQ ID No. 10), F5/R3 (SEQ ID No. 15/SEQ ID No. 12), F6/R3 (SEQ ID No. 16/SEQ ID No. 12), F7/R1 (SEQ ID No. 3/SEQ ID No. 8), and F7/R2 (SEQ ID No. 9/SEQ ID No. 10) F7/R3 (SEQ ID No. 3/SEQ ID No. 12).

DNA Gel Purification and Sequencing

PCR amplified DNA fragments were purified with the QIAquick kit (QIAGEN), according to manufacturer's instructions. Purified fragments were then sequenced by Sanger sequencing (Plate-forme de séquençage et génomique, Institut Cochin Paris). DNA sequences were then analysed with the biological sequence alignment editor BioEdit (http://www.mbio.ncsu.edu/bioedit/bioedit.html) and bioinformatics analysis was performed with the software BLAST (http://blast ncbi.nlm.nih.gov/Blast.cgi).

Results

We were able to successfully amplify two DNA fragments by PCR, specific for the cell-line 10799001 bearing the BRCA1 triplication, but not for the control cell-line 40, employing primer pairs F7/R7 and F9/R8 (FIGS. 3B-3C). An apparent 600 bp DNA fragment was amplified by PCR with the primers F7/R7, and an apparent 400 pb DNA fragment with primers F9/R8. Sequencing of the fragments resulted in 574 (primer F7), 561 (primer R7), 337 (primer F9) and 306 (primer R8) bases long DNA fragments. Bioinformatics analysis confirmed that the DNA fragment amplified by primers F7/R7 and F9/R8 was identical, with the F9/R8 being shorter than the F7/R7 fragment.

Sequence comparison with the reference human genome sequence showed that the amplified fragments were constituted by the region of intron 2 of BRCA1 extending from position 41,272,683 towards the telomere and the 5′ region of NBR2 extending from position 41,279,989 towards the centromere connected by a 48 bp sequence common to both positions 41,272,683 in intron 2 of BRCA1 and 41,279,942, in the 5′ region of NBR2 (FIG. 4). The 48 bp common sequence is as follows:

(SEQ ID NO: 21) GAGGCAGGAGAATGGCGTGAACCCGGGAGGCGGAGCTTGCAGTGAGCC.

This is perfectly compatible with the triplication of the 7.3 kb-sequence fragment comprised between these two positions, with the breakpoint occurring in a stretch of perfect sequence identity

Direct PCR Testing

Since PCR amplification using primer pairs F7/R7 and F9/R8 resulted in the amplification of PCR products in a control sample without amplification, we designed additional primer pairs that amplify products specifically in the sample bearing the amplification reported here.

As shown in FIG. 5A, fragments specific for the BRCA1 triplication were obtained out of 8 primer pairs (F1/R1, F1/R2, F1/R3, F2/R7, F5/R2, F5/R3, F6/R3, F7/R2), with sizes consistent with the relative location of the primers and breakpoints. Primer pairs F5/R2, F5/R3 and F6/R3 showed amplification products only in the mutation positive cell-line 10799001, but not in the control cell-line 38.

Additional samples, from three unrelated patients (coming from different French regions, also unrelated to the patient from whom cell line 10799001 was established) where an amplification had been suspected following aCGH testing, were submitted to PCR amplification with primer pairs F5/R2, F5/R3 and F6/R3. A specific PCR product was observed, with the expected size for the amplification reported here, which was not observed in control samples (FIG. 5B). These PCR products were sequenced and results were identical to cell-line 10799001. This confirmed the identical nature of the amplification, with the same breakpoint position, in four unrelated samples.

The primer pairs described here are examples of primer pairs that enable the specific detection of the reported breakpoint. Indeed, in a wild-type sample, the relative orientation of the forward and reverse primers of any of these pairs is such that no specific amplification is possible: the forward primer allows priming for a polymerization towards the centromere, while it is located upstream of the reverse primer. The tandem amplification brings an additional copy of the sequence corresponding to the forward primer (see FIG. 3). This additional copy being downstream of the reverse primer, the amplification of the sequence stretch between both primers becomes possible. Using such an approach, the man skilled in the art may design other primer pairs with equivalent properties. Such primer pairs must be constituted of

-   -   one forward primer (oriented from telomere to centromere)         located preferentially less than 5 kb, more preferentially less         than 2 kb, even more preferentially less than 1 kb and even more         preferentially less than 500 bp from the breakpoint location in         the BRCA1 gene (i.e. between genomic positions 41,279,990 and         41,284,990; preferentially between positions 41,279,990 and         41,281,990; more preferentially between positions 41,279,990 and         41,280,990 and even more preferentially between positions         41,279,990 and 41,280,490); and     -   one reverse primer (oriented from centromere to telomere))         located preferentially less than 5 kb, more preferentially less         than 2 kb, even more preferentially less than 1 kb and even more         preferentially less than 500 bp from the breakpoint location in         the NBR2 gene (i.e. between genomic positions 41,267,683 and         41,272,683; preferentially between positions 41,270,683 and         41,272,683; more preferentially between positions 41,271,683 and         41,272,683 and even more preferentially between positions         41,272,183 and 41,272,683); where     -   the forward primer is located upstream of the reverse primer.         Discussion

The amplification reported here is the first report of a sequence amplification in the region of BRCA1 comprising exons 1a, 1 b and 2 and the intervening introns, and the second triplication reported in the BRCA1 locus. Of note, this region of BRCA1 is very rich in repetitive sequences. The prior art relied on methods which have low detection capacity for such amplifications, either because they fail to cover regions rich in repetitive sequences, or because they fail to distinguish the copy number change induced by a triplication from that induced by a duplication.

Here, we show that using Molecular Combing or related direct mapping methods in such regions, it is possible to correctly detect and characterize such amplifications. The probe sets illustrated here are examples of probe sets which can be used for this purpose when using Molecular Combing. Adaptations of this design are possible and readily achievable by the man skilled in the art, whether for Molecular Combing or for related direct mapping methods. Using such methods, the amplification is typically detected either by a change in the succession of detected sequences or by an increase in length of the region of interest.

We also show that although in some regions such as the one involved in the triplication reported here, the presence of repetitive sequences makes specific PCR amplification challenging, with sufficient knowledge of the breakpoint location it is possible to obtain a product specific for the amplification. The nature of the product may be confirmed by sequencing, which unambiguously allows characterizing the resulting rearrangement.

The sufficient knowledge of the breakpoint location needed here may be obtained by careful analysis of mapping results obtained through Molecular Combing or related direct mapping methods.

In the case of the amplification of the region extending from intron 2 of BRCA1 to the 5′ portion of NBR2 reported here, which appears to be a recurrent event, the amplification may be immediately characterized by using previously validated primer pairs, such as the ones we disclose here. Besides, the precise description of the breakpoint disclosed here would allow a man skilled in the art to use an alternative method (or PCR using different primer pairs) for the detection of this amplification.

In cases where such amplifications are reported to be recurrent, i.e. to occur in unrelated samples, systematic screening may also be considered. Direct testing for these recurrent amplifications without prior mapping is likely to efficiently reveal such an amplification in a sample.

The following numbered paragraphs represent various embodiments of the invention:

-   -   1. A method for in vitro detection of large rearrangement in the         BRCA1 gene contained in nucleic acid of a biological sample         comprising nucleic acid representative of chromosomal nucleic         acid, in particular nucleic acid of human chromosome 17,         comprising the step of detecting multiple copies of a target         amplified sequence which is a sequence including exons 1a, 1b         and 2 of the BRCA1 gene in the human 17 chromosome.     -   2. A method for in vitro detection of large rearrangement in the         BRCA1 gene contained in nucleic acid of a biological sample         comprising nucleic acid representative of chromosomal nucleic         acid, in particular nucleic acid of human chromosome 17,         comprising the step of detecting multiple copies of a target         amplified sequence which is a sequence having a size in a range         of 6 kb to 8 kb and extending from intron 2 of the BRCA1 gene to         the 5′ end of the NBR2 gene in the human 17 chromosome.     -   3. A method for in vitro detection of large rearrangement in the         BRCA1 gene according to paragraph 1 or 2 which comprises steps         of:         -   providing the nucleic acid of the biological sample which             comprises the target amplified sequence in conditions that             enable hybridization with a probe or a set of probes, in             particular providing the nucleic acid of the biological             sample which comprises the target amplified sequence as             isolated nucleic acid;         -   contacting said provided nucleic acid with a probe or a set             of probes in conditions enabling hybridization of the             probe(s) with the target sequence, wherein each probe             hybridizes with all or part of the amplified sequence             extending from intron 2 of the BRCA1 gene to the 5′ end of             the NBR2 gene,         -   detecting signals corresponding to hybridized probe(s), in             particular by visualization.     -   4. A method for in vitro detection of large rearrangement in the         BRCA1 gene according to any of paragraphs 1 to 3, where the         detected amplified nucleic acid sequence is present in a copy         number of at least 3 successive copies, in particular a copy         number of 3 thereby characterizing a triplication in tandem of         the target amplified sequence in the biological sample.     -   5. A method for in vitro detection of large rearrangement in the         BRCA1 gene according to any of paragraphs 1 to 4, wherein the         detection of multiple copies of the target amplified sequences         comprises measuring the size of the nucleic acid sequence         hybridized to the probe(s) and comparing said measured size to         the size of the amplified sequence taken as a single copy which         is in a range of 6 kb to 8 kb.     -   6. A method for in vitro detection of large rearrangement in the         BRCA1 gene according to any of paragraphs 1 to 5, wherein the         nucleic acid representative of chromosomal nucleic acid, in         particular nucleic acid of human chromosome 17 is stretched         prior to contacting with the probe(s).     -   7. A method for in vitro detection of large rearrangement in the         BRCA1 gene according to any of paragraphs 1 to 6, wherein the         target sequence consists of the sequence extending from position         41,272,683 to position 41,279,942 in human chromosome 17 or a         sequence framed by nucleic acid sequences consisting of the 48         base pairs sequence at position 41,272,683 in the BRCA1 gene and         the identical sequence in the NBR2 gene.     -   8. A method for in vitro detection of large rearrangement in the         BRCA1 gene according to any of paragraphs 1 to 7 wherein the set         of probes comprises or consists of a mixture of probes         comprising Synt1 probe having a nucleic acid sequence base         pairing with a genomic sequence starting with nucleotide at         position 41,269,785 and ending with nucleotide at position         41,274,269 and S7 probe having a nucleic acid sequence base         pairing with a genomic sequence starting with nucleotide at         position 41,275,399 and ending with nucleotide at position         41,278,707, said probes being labeled with different markers or         labels, in particular with a marker or label enabling         visualization of a different color for each probe when detected.     -   9. A method for in vitro detection of large rearrangement in the         BRCA1 gene according to paragraph 8 wherein the Synt1 probe has         the sequence amplified by primers Synt1F (SEQ ID No. 17) and         Synt1R (SEQ ID No. 18) on a nucleic acid representative of the         human BRCA1 gene or has the sequence of SEQ ID No. 1 and the S7         probe has the sequence amplified by primers S7F (SEQ ID No. 19)         and S7R (SEQ ID No. 20) on a nucleic acid representative of the         human BRCA1 and NBR2 genes or has the sequence of SEQ ID No. 2.     -   10. A method for in vitro detection of large rearrangement in         the BRCA1 gene according to any of paragraphs 1 to 9, which         comprises the steps of:         -   providing isolated nucleic acid representative of             chromosomal nucleic acid that comprises the target amplified             sequence, in particular isolated nucleic acid of human             chromosome 17, in particular isolated genomic DNA of human             chromosome 17 in a combing vessel;         -   performing molecular combing on said nucleic acid; to             stretch the nucleic acid and provide physical mapping of             said stretched nucleic acid;         -   contacting combed nucleic acid with a labeled probe or a set             of probes wherein each of the probe hybridizes with a             distinct region of the target amplified sequence and is             labeled with a different label, in conditions enabling             hybridization of the probes with the target amplified             sequence;         -   washing the reaction mixture after hybridization;         -   detecting the signals corresponding to hybridized labeled             probes.     -   11. A method for in vitro detection of large rearrangement in         the BRCA1 gene according to any of paragraphs 1 to 10, wherein         the detection of signals corresponding to hybridized labeled         probes of a set of probes encompasses detecting hybridization         patterns and determining the succession of hybridized probes,         their identity and their length.     -   12. A method for in vitro detection of large rearrangement in         the BRCA1 gene according to paragraph 11, which further         comprises a step of comparing the detecting hybridization         patterns reflecting the succession of hybridized probes with the         theoretical hybridization pattern (i.e. the hybridization         pattern expected for a wild-type sample).     -   13. A method for in vitro detection of large rearrangement in         the BRCA1 gene according to any of paragraphs 1 to 4 which         comprises:         -   contacting the nucleic acid representative of chromosomal             nucleic acid comprising the target amplified sequence, in             particular nucleic acid of human chromosome 17, in             particular genomic DNA, of the biological sample, with one             or several set(s) of amplification primers wherein the             primers have a nucleotide sequence selected as follows:         -   one forward primer (oriented from telomere to centromere)             located preferentially less than 5 kb, more preferentially             less than 2 kb, even more preferentially less than 1 kb and             even more preferentially less than 500 bp from the             breakpoint location in the BRCA1 gene (i.e. between genomic             positions 41,279,990 and 41,284,990; preferentially between             positions 41,279,990 and 41,281,990; more preferentially             between positions 41,279,990 and 41,280,990 and even more             preferentially between positions 41,279,990 and 41,280,490);             and         -   one reverse primer (oriented from centromere to telomere))             located preferentially less than 5 kb, more preferentially             less than 2 kb, even more preferentially less than 1 kb and             even more preferentially less than 500 bp from the             breakpoint location in the NBR2 gene (i.e. between genomic             positions 41,267,683 and 41,272,683; preferentially between             positions 41,270,683 and 41,272,683; more preferentially             between positions 41,271,683 and 41,272,683 and even more             preferentially between positions 41,272,183 and 41,272,683);             and where         -   the forward primer is located upstream of the reverse             primer,         -   enabling PCR amplification or PCR-related amplification of             the target amplified sequence extending from exon 2 of the             BRCA1 gene to the 5′ end of the NBR2 gene,         -   detecting the PCR amplified nucleic acid fragments or             PCR-related amplified nucleic acid fragments and optionally             sequencing them.     -   14. A method for in vitro detection of large rearrangement in         the BRCA1 gene according to paragraph 14 wherein the primer sets         are selected in the group of primer pairs having nucleotide         sequences designated as F7/R7 (SEQ ID No3/SEQ ID No. 4), F9/R8         (SEQ ID No. 5/SEQ ID No. 6), F1/R1 (SEQ ID No. 7/SEQ ID No. 8),         F1/R2 (SEQ ID No. 7/SEQ ID No. 10), F1/R3 (SEQ ID No. 7/SEQ ID         No. 12), F2/R7 (SEQ ID No. 9/SEQ ID No. 4), F3/R4 (SEQ ID No.         11/SEQ ID No. 14), F3/R7 (SEQ ID No. 11/SEQ ID No. 4), F4/R7         (SEQ ID No. 13/SEQ ID No. 4), F5/R2 (SEQ ID No. 15/SEQ ID No.         10), F5/R3 (SEQ ID No. 15/SEQ ID No. 12), F6/R3 (SEQ ID No.         16/SEQ ID No. 12), F7/R1 (SEQ ID No. 3/SEQ ID No. 8), and F7/R2         (SEQ ID No. 9/SEQ ID No. 10) F7/R3 (SEQ ID No. 3/SEQ ID No. 12)         wherein the “F” primer is a forward primer and the “R” primer is         a reverse primer or are selected in the group of primer pairs         constituted by the reverse complementary sequences of the above         sequences in the primer pairs.     -   15. A method for in vitro detection of large rearrangement in         the BRCA1 gene according to paragraph 14 wherein the primer sets         are selected in the group of primer pairs having nucleotide         sequences designated as F7/R7 (SEQ ID No3/SEQ ID No. 4), and         F9/R8 (SEQ ID No. 5/SEQ ID No. 6) in the group of primer pairs         constituted by the reverse complementary sequences of the above         sequences in the primer pairs.     -   16. A method of in vitro determining predisposition to disease         associated with amplification of sequences in the BRCA1 locus of         human chromosome 17 in a biological sample obtained from a human         patient, which comprises performing a method of detection of         large rearrangement in the BRCA1 gene in said biological sample         according to any of paragraphs 1 to 16.     -   17. A method according to paragraph 17 for the determination of         predisposition to breast cancer or ovarian cancer, wherein said         predisposition is acknowledged when an amplification, especially         a triplication of the target amplified sequence is observed.     -   18. A method of determining or adapting medical follow-up and/or         treatment of a breast cancer or an ovarian cancer, which         comprises performing a method of detection of large         rearrangement in the BRCA1 gene in said biological sample         according to any of paragraphs 1 to 17.     -   19. A primer pair wherein the forward and the reverse primers         have respectively a sequence selected from:         -   for the forward primer (oriented from telomere to             centromere) a sequence located preferentially less than 5             kb, more preferentially less than 2 kb, even more             preferentially less than 1 kb and even more preferentially             less than 500 bp from the breakpoint location in the BRCA1             gene (i.e. between genomic positions 41,279,990 and             41,284,990; preferentially between positions 41,279,990 and             41,281,990; more preferentially between positions 41,279,990             and 41,280,990 and even more preferentially between             positions 41,279,990 and 41,280,490); and         -   or the reverse primer (oriented from centromere to             telomere)) a sequence located preferentially less than 5 kb,             more preferentially less than 2 kb, even more preferentially             less than 1 kb and even more preferentially less than 500 bp             from the breakpoint location in the NBR2 gene (i.e. between             genomic positions 41,267,683 and 41,272,683; preferentially             between positions 41,270,683 and 41,272,683; more             preferentially between positions 41,271,683 and 41,272,683             and even more preferentially between positions 41,272,183             and 41,272,683). A primer pair selected from the group of             primer pairs having nucleotide sequences F1/R1 (SEQ ID No.             7/SEQ ID No. 8), F1/R2 (SEQ ID No. 7/SEQ ID No. 10), F1/R3             (SEQ ID No. 7/SEQ ID No. 12), F2/R7 (SEQ ID No. 9/SEQ ID No.             4), F5/R2 (SEQ ID No. 15/SEQ ID No. 10), F5/R3 (SEQ ID No.             15/SEQ ID No. 12), F6/R3 (SEQ ID No. 16/SEQ ID No. 12) and             F7/R2 (SEQ ID No. 9/SEQ ID No. 10) or in the group of primer             pairs constituted by the reverse complementary sequences of             the above sequences in the primer pairs.     -   20. A mixture of probes comprising at least two labeled         polynucleotides wherein each of the polynucleotides has a         nucleotide sequence hybridizing with a nucleic acid sequence         from the region extending from intron 2 of the BRCA1 gene to the         NBR2 gene in human chromosome 17 and wherein each polynucleotide         is labeled with a different visually detectable label.     -   21. A mixture of polynucleotide probes according to paragraph         21, wherein the polynucleotides have a nucleic acid sequence         selected in the group of Synt1 (SEQ ID No. 1) and S7 (SEQ ID No.         2).     -   22. A kit for the detection of multiple copies of an amplified         sequence having a size in a range of 6 kb to 8 kb and extending         from intron 2 of the BRCA1 gene to the NBR2 gene in the human 17         chromosome in a biological sample comprising:         -   a primer pair selected from the group of primer pairs having             nucleotide sequences F1/R1 (SEQ ID No. 7/SEQ ID No. 8),             F1/R2 (SEQ ID No. 7/SEQ ID No. 10), F1/R3 (SEQ ID No. 7/SEQ             ID No. 12), F2/R7 (SEQ ID No. 9/SEQ ID No. 4), F5/R2 (SEQ ID             No. 15/SEQ ID No. 10), F5/R3 (SEQ ID No. 15/SEQ ID No. 12),             F6/R3 (SEQ ID No. 16/SEQ ID No. 12) and F7/R2 (SEQ ID No.             9/SEQ ID No. 10);         -   optionally, a detection probe for the PCR-amplified             nucleotide fragments,         -   reagents for conducting PCR amplification or PCR-type             amplification;         -   instructions for use and packaging material.     -   23. An isolated polynucleotide comprising at least two or at         least three tandem copies of a sequence, each copy having a size         in a range of 6 kb to 8 kb and corresponding to a sequence         extending from intron 2 of BRCA1 to the NBR2 gene in the human         17 chromosome.

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The invention claimed is:
 1. A method for in vitro detection of at least three successive copies of a target sequence in the BRCA1 gene contained in a nucleic acid of a biological sample comprising genomic nucleic acid of human chromosome 17, wherein the target sequence is a sequence having a size in a range of 6 kb to 8 kb and extending from intron 2 of the BRCA1 gene to the 5′ end of the NBR2 gene in the human chromosome 17, and wherein said method comprises: (a) providing the nucleic acid of the biological sample which comprises the target sequence, optionally as isolated nucleic acid; (b) hybridizing under stringent conditions said nucleic acid to a labeled probe or a set of labeled probes, wherein each labeled probe hybridizes with all or part of the sequence extending from intron 2 of the BRCA1 gene to the 5′ end of the NBR2 gene; wherein the labeled probe or the set of labeled probes is amplified by one or several set(s) of amplification primers having a nucleotide sequence selected as follows: one forward primer (oriented from telomere to centromere) located between genomic positions 41,279,990 and 41,284,990 of the human reference genome sequence build GRCh37/hg19 of human chromosome 17; and one reverse primer (oriented from centromere to telomere) located between genomic positions 41,267,683 and 41,272,683 of the human reference genome sequence build GRCh37/hg19 of human chromosome 17; and wherein the forward primer is located upstream of the reverse primer, enabling PCR amplification or amplification by a PCR-related method of the target sequence; (c) detecting signals corresponding to hybridized labeled probe(s); (d) comparing the resulting hybridization pattern reflecting the succession of hybridized labeled probes with the hybridization pattern expected for a wild-type sample; and (e) when said resulting hybridization pattern contains additional signals consisting of or comprising at least three identical patterns when compared to said hybridization pattern expected for a wild-type sample, concluding that the biological sample contains at least three successive copies of the target sequence.
 2. The method for in vitro detection of at least three successive copies of a target sequence in the BRCA1 gene according to claim 1, wherein the target sequence consists of the sequence extending from position 41,272,683 to position 41,279,942 of the human reference genome sequence build GRCh37/hg19 of human chromosome
 17. 3. The method for in vitro detection of at least three successive copies of a target sequence in the BRCA1 gene according to claim 1 wherein the set of labeled probes comprises a Synt1 probe having a nucleic acid sequence base pairing with a genomic sequence starting with nucleotide at position 41,269,785 and ending with nucleotide at position 41,274,269 of the human reference genome sequence build GRCh37/hg 19 of human chromosome 17 and an S7 probe having a nucleic acid sequence base pairing with a genomic sequence starting with nucleotide at position 41,275,399 and ending with nucleotide at position 41,278,707 of the human reference genome sequence build GRCh37/hg19 of human chromosome 17, said probes being labeled with different markers or labels, said markers or labels optionally enabling visualization of a different color for each probe when detected.
 4. The method for in vitro detection of at least three successive copies of a target sequence in the BRCA1 gene according to claim 3, wherein the sequence of the Synt1 probe is the sequence amplified by primers Synt1F with the sequence of SEQ ID NO: 17 and Synt1R with the sequence of SEQ ID NO: 18 on a genomic nucleic acid of the human BRCA1 gene or is the sequence of SEQ ID NO: 1 and wherein the sequence of the S7 probe is the sequence amplified by primers S7F with the sequence of SEQ ID NO: 19 and S7R with the sequence of SEQ ID NO: 20 on a genomic nucleic acid of the human BRCA1 and NBR2 genes or is the sequence of SEQ ID NO:
 2. 5. The method for in vitro detection of at least three successive copies of a target sequence in the BRCA1 gene according to claim 1, wherein the genomic nucleic acid of human chromosome 17 is a genomic DNA isolated from the biological sample and wherein said method further comprises: at (a), providing isolated genomic DNA of human chromosome 17 in a combing vessel; before (b), performing molecular combing on said genomic DNA to stretch the genomic DNA and provide physical mapping of said stretched genomic DNA; in (b), hybridizing combed genomic DNA with the labeled probe or the set of labeled probes wherein each of the probes hybridizes with a distinct region of the target sequence and is labeled with a different label, washing the reaction mixture after hybridization of (b).
 6. The method for in vitro detection of at least three successive copies of a target sequence in the BRCA1 gene according to claim 5, wherein the detection of signals corresponding to hybridized labeled probes of a set of probes encompasses detecting hybridization patterns and determining the succession of hybridized probes, their identity and their length.
 7. The method for in vitro detection of at least three successive copies of a target sequence in the BRCA1 gene according to claim 1 wherein the set of amplification primers is wherein the “F” primer is a forward primer and the “R” primer is a reverse primer, or is the pair of primers with reverse complementary sequences to the primers F5 and R2.
 8. The method for in vitro detection of at least three successive copies of a target sequence in the BRCA1 gene according to claim 7, wherein the set of amplification primers further comprise primer pairs selected from the group of primer pairs having nucleotide sequences designated as F7/R7 (SEQ ID NO: 3/SEQ ID NO: 4), and F9/R8 (SEQ ID NO: 5/SEQ ID NO: 6), the pair of primers with reverse complementary sequences to the primers F7 and R7, and the pair of primers with reverse complementary sequences to the primers F8 and R8.
 9. The method for in vitro detection of at least three successive copies of a target sequence in the BRCA1 gene according to claim 1, wherein said method further comprises a step of correlating the presence of at least three successive copies of the target sequence with a predisposition to a breast cancer.
 10. The method for in vitro detection of at least three successive copies of a target sequence in the BRCA1 gene according to claim 1, wherein the set or sets of amplification primers are selected from the group of primer pairs having nucleotide sequences designated as F7/R7 (SEQ ID NO: 3/SEQ ID NO: 4), F9/R8 (SEQ ID NO: 5/SEQ ID NO: 6), F1/R1 (SEQ ID NO: 7/SEQ ID NO: 8), F1/R2 (SEQ ID NO: 7/SEQ ID NO: 10), F1/R3 (SEQ ID NO: 7/SEQ ID NO: 12), F2/R7 (SEQ ID NO: 9/SEQ ID NO: 4), F3/R4 (SEQ ID NO: 11/SEQ ID NO: 14), F3/R7 (SEQ ID NO: 11/SEQ ID NO: 4), F4/R7 (SEQ ID NO: 13/SEQ ID NO: 4), F5/R3 (SEQ ID NO: 15/SEQ ID NO: 12), F6/R3 (SEQ ID NO: 16/SEQ ID NO: 12), F7/R1 (SEQ ID NO: 3/SEQ ID NO: 8), and F7/R2 (SEQ ID NO: 9/SEQ ID NO: 10) F7/R3 (SEQ ID NO: 3/SEQ ID NO: 12), wherein the “F” primer is a forward primer and the “R” primer is a reverse primer, or are selected from the group consisting of the pairs of primers with reverse complementary sequences to the sequences in the primer pairs above.
 11. A method for in vitro detection of at least three successive copies of a target sequence in the BRCA1 gene contained in a nucleic acid of a biological sample comprising genomic nucleic acid of human chromosome 17, wherein the target sequence is a sequence having a size in a range of 6 kb to 8 kb and extending from intron 2 of the BRCA1 gene to the 5′ end of the NBR2 gene in the human chromosome 17, and wherein said method comprises the steps of: (a) providing the nucleic acid of the biological sample which comprises the target sequence, optionally as isolated nucleic acid; (b) hybridizing under stringent conditions said nucleic acid to a labeled probe or a set of labeled probes, wherein each labeled probe hybridizes with all or part of the sequence extending from intron 2 of the BRCA1 gene to the 5′ end of the NBR2 gene; wherein the labeled probe or the set of labeled probes is amplified by one or several set(s) of amplification primers having a nucleotide sequence selected as follows: one forward primer (oriented from telomere to centromere) located between genomic positions 41,279,990 and 41,284,990 of the human reference genome sequence build GRCh37/hg19 of human chromosome 17; and one reverse primer (oriented from centromere to telomere) located between genomic positions 41,267,683 and 41,272,683 of the human reference genome sequence build GRCh37/hg19 of human chromosome 17; and wherein the forward primer is located upstream of the reverse primer, enabling PCR amplification or amplification by a PCR-related method of the target sequence; (c) detecting signals corresponding to hybridized labeled probe(s); (d) measuring the size of the nucleic acid sequence hybridized to the labeled probe(s); and (e) comparing said measured size to the size of the target sequence, wherein when said measured size is three times greater than the expected size of the target sequence, concluding that the sample contains at least three successive copies of the target sequence. 